Not so sure much of the backpressure loss argument holds much water if you're running the factory Y pipe.

 

How much backpressure should we have? Is there anyway that I can tell how much I lost? I'm sure its a good bit. My exhaust comes out in front of rear and its 3" for the muffler back.

 

If your running the stock cat or the stock Y- pipe its not going to make a difference. The bottle neck that the stock cat and Y-pipe takes care of the backpressure. In theory, we (5.9) should not be going above 3" piping for single or 2.5 for d/o. Youve seen my 2.5 d/o and mines fine. I have magnaflow cat too, the Y-pipe has that bottleneck still there (thats going to be fixed soon enough). Then we move on to the heads......

 

Yea but yr muffler is like stock size. Mine is not. I still have the factory cat and y pipe. Now how to go about fixing that y pipe? Which kinda of headers do you have?

 

Back pressure is a myth that you don't need to worry about. No back pressure is good back pressure. The better your engine can breath the better it runs and the more power it creates.

 

doesnt matter if its close to stock size. Its still a higher flowing muffler. Get a more free flowing Y-pipe, and i have gibson ceramic coated shorties.