Long-time lurker, purchased a 07 DG 6MT coupe a year ago. Finally got around to modding it when the stock cats started throwing codes. Installed the Megan test pipes (resonated), and noticed the hiss/rattle as revs wind down around 2400-2500 rpm.

I went up on the lift with the car as my assistant (Toyota tech) was under it hunting for the noise. He found that it was actually coming from the stock y-pipe, where the two converge. Removed the heat shield from the y-pipe, and the one near the passenger side test pipe. No change. New y-pipe on the way.

 

Is it raspy? or like a hiss? It's usually caused by a difference in the diameter of piping I believe. Someone correct me if I'm wrong?

 

The overall exhaust tone is more raspy, but not in a bad way. That said, if it got more raspy I would be replacing things. The sound in question is more like a hiss, and only as the engine winds down around 2500 rpm. There is also a hiss (different) that picks up after 3000 when WOT. The best way to describe that, and I hate to use it as an example, is a sound like a turbo car when WOT.

 

The "hiss" when the engine winds down is very common with test pipes.

I used to have Megan V2 test pipes and an X02 and it went away after I installed a Magnaflow resonated x-pipe.

 

There's a cat in the stock Y if i remember correctly or you could have a piece of cat floating around in it...rip that heavy thing off

 

the hiss is from the flex sections in the y pipe. the rasp is because the stock cats act as resonators, taking them out adds flow and raps. Too much rasp for whatever resonator you have on the exhaust system.

 

Is that going to be a hiss with any y-pipe, or simply the stock one? Resonated test pipes aside, the exhaust is otherwise stock.

 

I have had a DE, HR, and m2 y pipe and they all have hissed.