I have a lifted 4WD 99 GMC Jimmy 4door and I have a curious question on the exhaust set up I want. I want to get a dual inlet muffler and get rid of the y pipe in the front. I want to have 2 separate pipes coming from the manifolds with a hi flow cat on each to go into a dual inlet flowmaster super 44 with dual outlet. Now would getting rid of the y pipe hurt my performance or better it? Also how would it effect the sound? And I was curious on if i could make the piping 2 1/2 inches instead of 2 1/4. And how would that effect the performance and the sound? And just out of curiousity, Would getting a cold air intake effect the sound? And what if i got a throttle body spacer? If this is not worth the trouble, then I'll probably just get a cat back system. Any advice will be appreciated.

 

I see you never got any reply's so I'll give you a bump cus I just acquired a '99 Jimmy. I'll be doing exhaust also. I have a guy that does custom exhaust so I'll be getting his advice this week on Wednesday or Thursday. (on vacation from Wednesday to Saturday). My plan is to run 2.5 through 2 different free flowing mufflers. I may have to get him to weld in 2 cats. I work at Advance Auto Parts so I can get the universal cats fairly reasonable.


The same guy put duel exhaust on my '06 V6 Magnum. He made 2 pipes to replace the Y pipe, put 2 flowmaster 40s on, then made the 2 tailpipes with 18" SS tips. All for $400.