i haven't seem much pics of a stock y-pipe, much less have seen the one on my car. but from what i have seen in the warpspeed, budget etc. y-pipes, is a straight pipe that has a smaller "pre-cat" at the end of the pipe. so i take it that the stock y-pipe has a "pre-cat" as well. if so, could someone "hypothetically" gut out the stock y-pipe and maybe get a few extra HP. i may not really do it if possible, i'm just curious and bored.

 

Aftermarket y-pipes dont have any precats.....your proabably thinking of the flex section, and the stock y pipe has 2 precats

 

Aftermarket Y-pipes does not have a pre-cat, thats the flex section you see. I dont think its possible to gut out a stock y-pipe because that thing is made out of cast metal.