I just installed the GMPP manifold and hahn downpipe/high-flo cat, and a hiss noise is emitted from the exhaust at moderate to high acceleration. I dont believe there are any leaks, i checked numberous amounts of times and no carbon or air felt/seen/heard coming from any part of the exhaust. At an Idle I can hear possibly a slight hiss at the post converter HO2S.

Has anyone come across this with either the GMPP manifold or Hahn downpipe? at this point im lost, please help.

Thanks!

 

Ets yewr turbah spewlen.

But seriously... not sure. Maybe it's just your intake sucking air in.

 

I had a hissing noise coming from my engine once it turned out to be a busted o-ring on one of my injectors is it really loud or not b/c my injector/o-ring problem caused a huge hissing noise and that might be it, otherwise i'd say check your seals again (where you're header meets with your cat back) and it might be because you just put it on other than that i have no idea.

 

im pretty sure its exhaust related, an injector 0-ring hiss would mean an intake leak which would cause it to run like ****. It runs mint, just under moderate to high acceleration you can hear it hiss.

 

Feel, not sound, is the best check for a leak. Physically hold your hand around each of the joints while running at idle. You will feel the air leak.

 

boostfr33k and I also have this noise and its related to the GMPP manifold. Ive checked for leaks and found nothing. Im still stumped but it still seems to run A-1.

 

no ****, i wonder if its a mistake we made or if it is a defect, or normal.