performance between just a muffler and a catback

[sfsc]

I liked my Flowmaster 40 when I picked it out 2ish years ago, but as time goes on it's losing its charm and its starting to sound less throaty and more droney. I decided on a Dynaflow Ultraflow after hearing it on a friend's 4.3 Blazer and after checking and seeing it actually is a boost in performance over stock versus just being a noise piece (read: FM40).

When I had my Flowmaster put in, I just bought the muffler and had a muffler shop slap it in for me for $50. The rest of the exhaust is stock.

They make a 2.5" catback system for $350ish bucks that's a has a Ultra Flow Muffler (SI/DO) with dual 3" tips. From the research I've done between here and S10 forums, there's no real reason to go dual with the 4.3 from a performance standpoint.

Dual exhaust looks nice and all that ... but would I really be getting any noticeable loss in power if I just have the shop slap in a SI/SO Dynomax versus buying that catback setup? I haven't crawled under and double checked and I can't remember from buying my FM40, but isn't the stock exhaust piping 2.5" anyway?

[1988 GMC 355]

You will gain performance compared to that FM, just have it welded in like you have the FM now, and cut that tailpipe off too :D

[Boy&hisDogs]

but what about cat-back vs just a muffler? I mean, does a stock 350 or 327 even need mandrel bent, larger diameter pipes? Hotter exhaust is higher pressure and easier to move, and ideal gas law says that smaller volume (smaller diameter pipes) equals more heat and pressure. Mandrel bending seems really unnecessary with a stock daily driver.

This is all assuming that the same muffler is used cat back or not.