I'm at a loss as to why everyone spends the time and effort to upgrade to 3" exhaust systems that bolt on AFTER the very restrictive factory Y-pipe that comes out at 2 1/2". It gives the same affect as adding a 6" tip on your tailpipe, nothing. Sure it gets rid of the factory fluffy muffler, and it is this replacement that gives a more free flowing system. You want to do it right, replace the factory Y with a dual 2 1/2" in and 3" out or go dual exhaust.
Has anyone actually looked inside that factory Y-pipe? You'd be surprised at how small that drivers side pipe really is.

 

thats what I said at first about removing it ( all the restrictiveness of the stock y) but everyone says these trucks need back pressure, that seems like a lot of back pres. I said it before I had an 01 gt and replaced the factory h with an o/r x and that thing really came to life. I know they are 2 different motors as far as intake and cam but I just dont know about 4 cats and small restrictive pipes, I guess I'll see how it feels with the muffler than if I am not happy I'll just change it up