Cons of removing cats?

[DarkCharisma]

Edit: okay, different approach. I am looking at purchasing some new cats, what's the length I need? Is there really any difference between a Magnaflow and an eBay cat? And, is $65 a good price for one?

My cats rattle something terrible but I don't have the money for new ones, and they're starting to butcher my mileage. If I remove them, will the sensors throw a code? Also, what will it do for power/economy? I've heard they lose low-end when removed/gutted.

I'll get new ones, but I can't afford to dump $200 on converters right now.

[DarkCharisma]

Nobody knows?

[Koots]

I would just gut them for now, if you can't afford new ones.
Yes the O2 sensor will throw a code, it's nothing serious if you can live with looking at it all day (i can)
You will lose a little low end torque, but with a clogged cat, you will restore some of the power from the restriction.

I've gone cat-less with every vehicle i have owned, not because i wanted that 1hp or 2 just because i was poor, like you. still am actually, gutted the cat on my truck and the Civic has no cat.

[RAPID]

I dont run cats either. When the service engine light comes on its just telling you the reading from the front and rear 02s are the same...Which they arent suppose to be. Not a problem. You can live with the light, OR, later on get a ECM tune that eliminates the rear 02 reading OR on many vehicles you can partially shield the rear 02 sensor to fool the computer into seeing a restricted flow and therefore a different reading. thus turning the light off. This mod is shown on different online websites and even works on New Hondas.

[Koots]

I dont run cats either. When the service engine light comes on its just telling you the reading from the front and rear 02s are the same...Which they arent suppose to be. Not a problem. You can live with the light, OR, later on get a ECM tune that eliminates the rear 02 reading OR on many vehicles you can partially shield the rear 02 sensor to fool the computer into seeing a restricted flow and therefore a different reading. thus turning the light off. This mod is shown on different online websites and even works on New Hondas.

Just go to the local parts store and get whats called a spark plug non-fouler and get it welded into the bung. it will put your O2 sensor partially out of the path of the exhaust so that it gets a lower reading than the primary sensor(s) and thinks that the cat is fine and/or present.

[Atomic]

Pros:
- Better high-end power
- Louder
- Less restriction for FI

Cons:
- Weaker bottom-end
- Louder
- Smells like ass
- Possible emissions problems
- It is a federal crime to remove them


Having had mine hacked off for about a year, I want them back, but I dont know how I can get that to work with the longtube headers.

[bizzy260]

take em off sell em to a core buyer ..large GMs go for bout $100-$150 each:eek: ...then buy some aftermarkets for less than you get for the shytty ones.....buy beer with the rest......:cool:

[thiems]

Having had mine hacked off for about a year, I want them back, but I dont know how I can get that to work with the longtube headers.
Um...you just weld some back in.

If your cats are bad and you can't get new ones just go without them for awhile. It won't be so loud that you will get stopped for them. Hell, I ditched mine a while ago and I don't miss them at all...

[heavy454]

Not the thread-jack or anything, but where can you go to sell your cats? i would cut my factory ones out and use the money for aftermarket ones if i got good money out of them

[Atomic]

Um...you just weld some back in.

If your cats are bad and you can't get new ones just go without them for awhile. It won't be so loud that you will get stopped for them. Hell, I ditched mine a while ago and I don't miss them at all...

Seeing as how you have the same pre-muffler setup as I do, do you mind providing pics? I couldnt easily see how where or how they would fit back in.

[GIMECHANIC_454]

The cats are gutted on my truck i have a 2K K2500 CCSB with 7.4L vortec, when i went threw and upgraded my exhaust i made my truck true dual exhaust (instead of dual in single out) i went from 2 3/4 to 3" all the way back to the bumper from behind the cat ran 2- 3" 40 original series(delta-flow)flowmasters and it lost a slight amount of low-end grunt(take-off)but the top end was improved silightly. (not a bad trade off) plus i have no codes come up from my O2 sensors.. anyway the point i am trying to make is the gutted cats should not affect the O2 sensors

[Koots]

Only O2 sensor it will affect is the Heated sensor (HO2 sensor) with all of the OBS (96 and up) their should be 2 primary sensors (bank 1 and bank 2) and an after cat (the heated) sensor. the after cat one is only to measure the cats effeciency at reducing emissions. If they get the same reading as the front sensors than that will send a code off to the ECM, which will not effect engine performance, but will set of a CEL. I have yet to see an OBD-II vehicle not give off a CEL with this procedure, but i can never say never but the CEL is the most common occurance.

If you can live with the light illuminating, you will be fine. The only bad part is you will not know if another DTC is reported unless you have access to a scan tool (I do which is why i don't pay any attention to the light) to check periodically for new codes. If the light doesn't come on afterwards than don't worry about it, but i would rather you be prepared for it when it does with the knowledge and a solution.

And if you already knew this before, i apologize for the long post :rocking:

[Koots]

Edit: okay, different approach. I am looking at purchasing some new cats, what's the length I need? Is there really any difference between a Magnaflow and an eBay cat? And, is $65 a good price for one?


Ebay "catalytic converters" are typically resonatored test pipes that fit in place of the stock cat. they have built in muffler so that they appear to be a fully functioning cat and quiet down the exhaust as to not draw any attention to you from the police.

Any universal cat (real functioning one) that has the right size inlets and outlets for your application should be fine. It's not really that big of a deal and will be cheaper than a OEM or aftermarket direct replacment one. It will just take a little modification from you or the local muffler shop.

[DarkCharisma]

Ebay "catalytic converters" are typically resonatored test pipes that fit in place of the stock cat. they have built in muffler so that they appear to be a fully functioning cat and quiet down the exhaust as to not draw any attention to you from the police.

Any universal cat (real functioning one) that has the right size inlets and outlets for your application should be fine. It's not really that big of a deal and will be cheaper than a OEM or aftermarket direct replacment one. It will just take a little modification from you or the local muffler shop.

Oh I see. Well for the same money I'll steer away from eBay cats and just start saving up for some Magnaflow cats I saw for $65 on Summit and have a shop weld them in.

Goddamn it that was supposed to be my tip 'n muffler money. :nopity: Thanks for your input guys.

[19doug90]

i honestly dont see your engine losing any low end power from gutting the cat. I guess youre removing a little bit of back pressure but the motor would breathe so much better everywhere, i bet if anything you would pick up a little low end power, and a lot of top end power.

i had a clogged cat in a car and gutting it is compairable to pulling a tennis ball out of your exhaust system.

If your exhaust system is appropriatly designed then you shouldnt need any added backpressure of a cat plugging things up.

i also agree that cats are stupidly expensive, high flow ones go for around 200 and the low profile high flow ones in the 250 range.
waaaay too much to spend on a piece of emissions equipment. Right now my camaro has long tubes with no cat's cause i just couldnt afford to buy them after everything.
And with my yukon id like to run long tubes and true duals but dual cats sucks

[BasicBlack]

I agree... there is no way removing cats will cost you low end power. With the location of the cats whats really happening is you are improving the scavenging of the exhaust system. With the better scavenging you are not LOSING power, simply moving the rpm band higher. Your probably just feeling the different power band you have created, and it feels like lower-end power loss.

[Atomic]

Low end power is more dependant on exhaust velocity, instead of total flow.

[Koots]

I agree... there is no way removing cats will cost you low end power. With the location of the cats whats really happening is you are improving the scavenging of the exhaust system. With the better scavenging you are not LOSING power, simply moving the rpm band higher. Your probably just feeling the different power band you have created, and it feels like lower-end power loss.

The scavenging effect of the exhaust on the intake mixture is wholly dependant on exhaust gas velocity. If you match the exhaust size to the engines output and needs, than the scavenging effect will work to your advantage. if you start increasing the exhaust size you may reduce restriction but go too far and the effect is lost. With the shift in powerband you describe, you are actually losing low end power because of the shift and putting it more in the midrange. you answered a question and contradicted your own post.

Sorry if i don't make much sense in my post but i've been up for 31hrs straight and my ADHD has gotten worse over the last few weeks hehe.

[PHATSPEED7x]

I've been running no cat for about 2 months now. Did get a louder tone, but I have a small leak that's driving me up a wall. Thinking of getting a high flow cat, and having a shop weld it in.

[19doug90]

Sorry if i don't make much sense in my post but i've been up for 31hrs straight and my ADHD has gotten worse over the last few weeks hehe.

i got a good laugh out of that, but its also 5 am :rocking:


I agree... there is no way removing cats will cost you low end power. With the location of the cats whats really happening is you are improving the scavenging of the exhaust system. With the better scavenging you are not LOSING power, simply moving the rpm band higher. Your probably just feeling the different power band you have created, and it feels like lower-end power loss.

I actually completly disagree with your post. Your post is exactly what theyre talking about. When you move an engines RPM powerband higher you lose power at low rpms.

I dont see removing your cat moving your engines powerband even 100 rpm. Infact if you have a well designed exhaust thats designed to make torque, then removing a partially plugged cat is just unplugging the exhaust system and allowing it to do what it should be doing.

Unplugging any exhaust system like that, unless you have 3" tubing coming off both sides is just going to give you more power everywhere.

[DarkCharisma]

Okay, with all this being said, who do I gut one? :dunno:

[19doug90]

Okay, with all this being said, who do I gut one? :dunno:

lol thats the answer every gearhead eventually comes to when it come to what to do with a potentially clogged cat.

ive never actually done it before tho, always wondered what the best tool to do it with is

[Atomic]

i got a good laugh out of that, but its also 5 am :rocking:




I actually completly disagree with your post. Your post is exactly what theyre talking about. When you move an engines RPM powerband higher you lose power at low rpms.

I dont see removing your cat moving your engines powerband even 100 rpm. Infact if you have a well designed exhaust thats designed to make torque, then removing a partially plugged cat is just unplugging the exhaust system and allowing it to do what it should be doing.

Unplugging any exhaust system like that, unless you have 3" tubing coming off both sides is just going to give you more power everywhere.


No. Like we said before. Low-end torque depends on exhaust VELOCITY, not volume. Which means smaller pipe (or pipe with cats) while be better at low-end but will struggle up top.

[BasicBlack]

We are all right in our views. I did contradict myself in my own post. The low-end torque will be lost at the expense of higher power up top. But, as 19doug90 said, I can't see the rpm band moving when you remove the cats. With smaller pipes the exhaust velocity causes the scavenging effect to occur lower in the rpm range. Bigger pipes mean higher rpm scavenging because of slower velocity at lower rpm's. That's what I was thinking, I just didn't have it in the right context. So now that we are on the same page, (we are aren't we?) we can get to point.

Take the cats off and use a plasma cutter to cut a big rectangular hole in the top of the case. What's inside I have no idea. Keep using the plasma or a grinder or what ever you got and get the stuff outta there. When your done weld the piece you cut off back on and reinstall. Make sure you put it on so you can't see it and you pass visual inspection if you have that kind of stuff. Good luck and let us know how it turns out.

[19doug90]

No. Like we said before. Low-end torque depends on exhaust VELOCITY, not volume. Which means smaller pipe (or pipe with cats) while be better at low-end but will struggle up top.

well ya and we get velocity from backpressure, so backpressure is a good thing.

what i said was assuming you have a well designed exhaust system, meaning the system is designed to provide the backpressure you need.

the partial clog of a cat is not really gaining you low end torque. id be welling to bet if you put a piece of straight tube in place of a cat you dont lose much of any low end torque if any at all, and gain power up top.

hey maybe just all that extra power up top will just make your bottom end feel slower.

lol thats just my opinion tho, hey maybe im wrong

[Atomic]

Let me explain my exhaust setup:

I have longtube headers, no cats, to a 3" offroad y pipe, directly after the y pipe is a 3.5" electric cutout. After that is a 36" mangnaflow muffler, and single 3" pipe out the back. Pretty straitforward setup (literaly).

With the cutout open, it is very obvious I have less power off-idle and down low, but I have more from 60+ mph versus with the cutout closed. The difference is significant enough to be noticeably felt.

I feel the same situation of no-cats vs cats is comparable to my cutout open vs muffler.


The easiest way I've heard to gut a cat is to cutout it out and take a steel bar and ram it in until its guts fall out and then weld it back in.

[Koots]

well ya and we get velocity from backpressure, so backpressure is a good thing.

what i said was assuming you have a well designed exhaust system, meaning the system is designed to provide the backpressure you need.

the partial clog of a cat is not really gaining you low end torque. id be welling to bet if you put a piece of straight tube in place of a cat you dont lose much of any low end torque if any at all, and gain power up top.

hey maybe just all that extra power up top will just make your bottom end feel slower.

lol thats just my opinion tho, hey maybe im wrong

I do understand the point you are trying to make, but backpressure is not what gives us our low end torque, it's exhaust gas velocity and the scavenging effect. you got the rest of it in context but it's not called that and some people will flip if they hear it. Back pressure has a negative effect on power production and is very different than a restriction. Just wanted to get the right words in the right places.

I don't mean to offend, IMO we are :thumbup: :cool:

[Z71Truckin]

I took my cats out of my 4.8l '99 z71 bout 2 months ago. You get about a 20 hp gain & better throttle response. Also i noticed MPG gained since my truck breathes a **** load easier. Only bad thing is since i have a single glasspack its louder as hell. Ill be gettin flowmasters to make it sound deeper & dampen the sound a tad bit. I have dyno papers to prove that i got a good gain. i just have to find them. I thought twice about gettin it done cause i thought the hp gain would make me lose mpg but it increased & i dont regret doin it.

[Koots]

I'm not doubting that the removal of the catalytic converters increase power, but i think you had such impressive gains because they may have been clogged up. Even when brand new you can experience a gain due to the reducing of backpressure but not a 20hp gain. There must have been other factors in play there.

[19doug90]

I'm not doubting that the removal of the catalytic converters increase power, but i think you had such impressive gains because they may have been clogged up. Even when brand new you can experience a gain due to the reducing of backpressure but not a 20hp gain. There must have been other factors in play there.
a VERY badly clogget cat is probably the explenation to that

[19doug90]

I do understand the point you are trying to make, but backpressure is not what gives us our low end torque, it's exhaust gas velocity and the scavenging effect. you got the rest of it in context but it's not called that and some people will flip if they hear it. Back pressure has a negative effect on power production and is very different than a restriction. Just wanted to get the right words in the right places.

I don't mean to offend, IMO we are :thumbup: :cool:

and i still disagree, but thats okay because this is how i learn stuff, although i think we in the end might be saying the exact same thing anyways.

Let me explaint his to the best of MY understanding and feel free to correct whatevers wrong

backpressure is an important function of the scavenging effect. If you were for arguements sake to have an 8" exhaust system you would have little to no backpressure, pressure inside the exhaust would be borderline atmospheric and you would have horrible scavenging qualities.

Now your arguement in the first place was that removing a cat would cause a loss in low end power. The only way that is possible is that the cat is causing a greater amount of backpressure in the system before the cat by being there, causing greater scavening qualities initially at least, and more low end torque.

My arguement is that by removing the cat that any loss in backpressure you would lose is negated by the fact that now you dont have a restriction in the exhaust system.

and on top of that if you have a 2.5" exhaust system that gives your motor the backpressure it needs to get good scavenging qualitites, you wouldnt even need that extra backpressure from the cat, and in fact would probably gain more power everywhere from removing a restriction

am i wrong?

[Koots]

You've got the concept correct but the terminology is what is wrong. Backpressure is commonly used to describe the scavenging effect, but the term backpressure is wrong here, not the concept but the word in context itself.

Here is a good tech article i found on another forum i frequent:

Backpressure:the myth and why it's wrong (http://www.hondacivicforum.com/m_39893/tm.htm)

And here is another on catalytic converters that has some good info but it's for honda engines which are highly tuned from the factory so the gains will be more noticeable on our trucks.

The Truth About Catalytic Converters (http://www.importtuner.com/features/0610impp_catalytic_converter_removal/index.html)

[19doug90]

You've got the concept correct but the terminology is what is wrong. Backpressure is commonly used to describe the scavenging effect, but the term backpressure is wrong here, not the concept but the word in context itself.

Here is a good tech article i found on another forum i frequent:

Backpressure:the myth and why it's wrong (http://www.hondacivicforum.com/m_39893/tm.htm)

And here is another on catalytic converters that has some good info but it's for honda engines which are highly tuned from the factory so the gains will be more noticeable on our trucks.

The Truth About Catalytic Converters (http://www.importtuner.com/features/0610impp_catalytic_converter_removal/index.html)

ah pretty obvious where im wrong there, good article.

this is cool definitly learned something today.

so how does the arguement for the cat come into play, because i could see the cat only causing a decrease in flow, and possibly cause a little backpressure if anything.

so why do you think you would lose low end torque

although its probably also true that the exhaust system thats going to give you the most torque with no backpressure at 1500 rpms is not going to be large enough not to cause backpressure at 5500 rpms, so i guess thats where you lose on one or the other

[TEE]

Not really...you ever looked at the honeycomb inside a cat? I doubt it would impede that much flow unless it was partially clogged.

[Dropkick13]

Let me explain my exhaust setup:

I have longtube headers, no cats, to a 3" offroad y pipe, directly after the y pipe is a 3.5" electric cutout. After that is a 36" mangnaflow muffler, and single 3" pipe out the back. Pretty straitforward setup (literaly).

With the cutout open, it is very obvious I have less power off-idle and down low, but I have more from 60+ mph versus with the cutout closed. The difference is significant enough to be noticeably felt.

I feel the same situation of no-cats vs cats is comparable to my cutout open vs muffler.


The easiest way I've heard to gut a cat is to cutout it out and take a steel bar and ram it in until its guts fall out and then weld it back in.

I know we are talking about cats vs no cats, but I can vouch for Atomic's statement as well. I too have a cut out post-cat / pre-muffler (still have cats and have a magnaflow muffler). There is a certain street that I run my truck on from a stop between two signs roughly (very roughly) 1/4 mi apart. With cut out open (no muffler), I get 81-83 mph while with it closed (with muffler) I get 83-85 mph. I also notice much better fuel mileage on the highway WITH my muffler. I have absolutely no idea why this is, but countless tanks of gas on the same road trip are evidence enough for me.

I too consider gutting my cats, but I really don't want to take my mileage down even more. What are the effects, do you think?

[19doug90]

I know we are talking about cats vs no cats, but I can vouch for Atomic's statement as well. I too have a cut out post-cat / pre-muffler (still have cats and have a magnaflow muffler). There is a certain street that I run my truck on from a stop between two signs roughly (very roughly) 1/4 mi apart. With cut out open (no muffler), I get 81-83 mph while with it closed (with muffler) I get 83-85 mph. I also notice much better fuel mileage on the highway WITH my muffler. I have absolutely no idea why this is, but countless tanks of gas on the same road trip are evidence enough for me.

I too consider gutting my cats, but I really don't want to take my mileage down even more. What are the effects, do you think?

i think your question comes into why length of an exhaust system is also important, opening it up half way makes a big difference to how far it has to go to reach somewhere with atmospheric pressure

[Dropkick13]

but would gutting cats also hurt gas mileage?

[19doug90]

but would gutting cats also hurt gas mileage?

i say it wont hurt either, if you care buy a high flow cat and its zero restriction and has no effect on the motor in any way.

just design an exhaust system that gets you optimal power and gas mileage

[Dropkick13]

I don't mean to thread jack but this is on par with "Cons of gutting your cats"

Anyway, would you have thought that running a cutout pre muffler would hurt mileage? I would not have (but I'm a moron), especially on the highway

[Koots]

ah pretty obvious where im wrong there, good article.

this is cool definitly learned something today.

so how does the arguement for the cat come into play, because i could see the cat only causing a decrease in flow, and possibly cause a little backpressure if anything.

so why do you think you would lose low end torque

although its probably also true that the exhaust system thats going to give you the most torque with no backpressure at 1500 rpms is not going to be large enough not to cause backpressure at 5500 rpms, so i guess thats where you lose on one or the other

With the catalytic converter, it is a restriction that does not cause backpressure. a brand new cat will allow a sufficient amount of air flow through (it's a misconception that it's so restricitive) with this restriction, it allows the exhaust gas velocity to remain high at low rpm and engine load allowing the engine to scavenge out the exhaust gas from the combustion chamber and with that vacuum effect suck in more intake charge during the valve overlap.

What this in turn does is cause the high rpm power to suffer, but for most truck users that doesn't make a difference as the low end torque is what the truck is made for. The older TBI heads were very restrictive but created loads of torque down very low, but were sucked out past 4000rpm and higher. Open up these ports and the velocity at low rpm's will drop but the potential volume will increase. but without the increase in fuel, air and exhaust breathing, this will hurt power production where it's most commonly needed in a truck application.

A new cat is not very restrictive so the low end loss isn't so noticeable when you remove it, but an older one with a bit more build up will cause a noticeable shift in powerband, due to the fact that you drive the truck for so long and get used to the powerband that a slightly clogged up cat creates. If you were to dyno your vehicle brand new, after 100k miles and than remove your cat the first and last runs will not differ dramatically (other than normal wear and tear power losses) but the difference between the first and second will show a torque gain with a top end drop, due to the clogging of the cat.

So it does create a mild shift in your powerband (mild as in not a whole lot) if the cat is old and clogged up, but will only bring the engine back to breathe a little easier than it did out of the showroom. clogged cats can restrict the exhaust to the point where you lose a couple MPG's, so you have to take that into account as well when you measure the effects of removing or gutting your catalytic converter.

[TruedualDD32]

This is a very informative and interesting thread.

So what would be a typical mileage at which one should consider replacing or removing the cats due to build-up?
Are there any tell tale signs to alert the driver?

[Koots]

This is a very informative and interesting thread.

So what would be a typical mileage at which one should consider replacing or removing the cats due to build-up?
Are there any tell tale signs to alert the driver?

If the secondary (heated) O2 sensors don't give off a CEL or DTC for cat inefficiency, than a drop in power and gas mileage would be the next sign. it will degrade over time to the point where you wouldn't notice it, being the primary driver, but the cat is clogging up the more you drive it. but don't point directly at the cat if these symptoms arise, because many other factors can cause such losses.

Your service manual or dealership should have an estimate as to when everything should be changed. Most of the time it's not until after 100k but it varies depending on a bunch of factors. If you have access to an OBD-II scanner reader with sensor readout and display to see if what the sensor is reading during closed loop operation. than compare that data with the recommended sensor readouts are to see if the cat is clogged up or whatnot.

[TruedualDD32]

Thanks for the info, I will have to get those readings checked out. I used crc maf cleaner this fall and noted about 1.5 mpg increase, so will check the exhaust next. The truck has 170,000 km on it now.

[BasicBlack]

Very good job explaining things Koots. I still want to cut a cat. apart with a plasma cutter, I love those things!! Anyone got one I can try? On secong thought maybe I will just do the one off my truck.

[Koots]

No problem, glad i could help :D
I am currently running a gutted cat on my truck (clogged the hell up)
and no cat on my Civic, but i'm gonna buy one at the end of the month because it is too damn loud. If it wasn't for the header and magnaflow muffler, it would be full out ricer, sound wise.

[93ChevyTBI]

I'm debating over putting cats back on mine as well...same reason...too loud. It's cheaper than putting all new flowmaster 50 series on. Around 1500 rpm it's droning, at 2000-2500 it's quiet. Over 3000 rpm and it's loud. My only question is why is it kinda loud droning at 1500??

[19doug90]

thats a good question, lol if its any consequence you get the same thing with open headers
1500-2000 is the most annoying drone in the world, get up to around 3000 and she purrrs

[93ChevyTBI]

What causes the drone anyway?? Better yet, what will stop it...putting cats back on or changing mufflers?

[Koots]

You get drone because the resonant frequencies normally deadened by the stock restrictive (sound and flow) mufflers would cancel out. When you have a perfromance muffler it doesn't deaden all of those sound waves and you get those odd rpm's in which it just vibrates the exhaust. I believe this is why, but i am no scientist :aniteef:

[BasicBlack]

Koots I think your on the right track with drone. I'm no rocket scientist either, but the frequencies and/or pulses of the exhaust have something to do with it. Corsa however DOES have a rocket scientist among them. Their mufflers do NOT have the dreaded drone. The C4 Corvettes, my 85, are notorious for resonance/droning. Think your truck is bad, let's go for a ride in my Vette, it gets annoying after 30 minutes. I have ridden in Corvettes with a Corsa cat-back and the difference is amazing!! Don't get me wrong, I like loud, but hate the drone!! And from my findings, cats will quiet down your exhaust, but adding an X or H pipe will not. They will change how they sound but not how loud they are.

[Koots]

Koots I think your on the right track with drone. I'm no rocket scientist either, but the frequencies and/or pulses of the exhaust have something to do with it. Corsa however DOES have a rocket scientist among them. Their mufflers do NOT have the dreaded drone. The C4 Corvettes, my 85, are notorious for resonance/droning. Think your truck is bad, let's go for a ride in my Vette, it gets annoying after 30 minutes. I have ridden in Corvettes with a Corsa cat-back and the difference is amazing!! Don't get me wrong, I like loud, but hate the drone!! And from my findings, cats will quiet down your exhaust, but adding an X or H pipe will not. They will change how they sound but not how loud they are.

Crossover pipes are meant to equalize the pulses between the bank so that the sound is smoother. Cats will help alot with sound deadening too as i have learned with my catless civic, but to help with the unwanted drone, adding a resonator will help remove the extra frequencies. I'm gonna go with a round casing magnaflow preferably with a long casing just to sweeten the tone, drop a few decibels and get rid of the drone.