GIMECHANIC_454
07-07-2007, 05:36 AM
I have a 2K Chevy Crew Cab 4X4 w/7.4L Vortec,(190K mi on the clock) the Cats on my truck are gutted, were gutted when I got it, its a 2 3/4" true dual to the muffler which dualled in and singled out(which I made it true dual all the way to the back) I also went from 2 3/4" to the Cat and from behind the Cat 3" pipe all the way out at a 45 deg under the back bumper and put Flowmaster Delta Flow original 40 Series mufflers 3" in- 3" out. I noticed alot of back pressure was lost, will not enuff back pressure cause really bad gas mileage and is it good on these Vortec engines? I have the pre-cat from dealership ($700 later) now I need to get the after-cat which is gona be at least another ($400). I did the exhuast back in March 2006 and have been running without cats since then, If I put the cats back on will that effect the way my engine runs? or will it damage the engine from not having back pressure for so long? any guidence will be helpful