Stock mid-pipe is 2 3/4 until it hits the muffler. When I first installed headers, I still had the factory mid pipe and muffler installed. When I swapped for the Phab cat back, the only difference I noticed was the sound. Power wise, I did not feel a change. The stock mid-pipe is not restrictive enough to notice anything.

 

with stock engine its not going to make much of a change, sound like said.

 

lol, this is what was on mine when i bought it.

 

I don't consider that the mid pipe. Mid pipe to me is cat to muffler. I consider that the y-pipe even as a stock application. Stock y-pipe is restrictive compared to aftermarket.

 

Same. On most store sites they call that the y pipe which it is. After that I consider the mid pipe between that and the muffler. That's the only part that's still stock on mine. That stock y pipe and manifolds are garbage lol.