Originally Posted by kfull

I've also noticed a faint hissing sound when idling since having my new x pipe installed. I can hear it in the cabin and outside the car mainly if I put my head right next to the right rear tire. It isn't a constant hiss, it's more like a short hiss at random intervals maybe every half second to a second. It's not very loud either, I really have to listen to even notice it. Is a hiss like that more common with a non resonated x pipe? I know where the x pipe is welded together it has the cross over hole so I was hoping its just air going across that hole. I hope it's not a leak. I had the shop use the existing gaskets like Tony said.