I have this not really loud hiss coming from my plenum/TB/front intake base area. BUT its only when the engine is really hot, I mean after I turn it on and let it sit idle you won´t hear anything…. It starts after a couple of minutes driving and you can only hear it “hiss” when the engine is off
It is not a vaccum leak because the car idles correctly. The upper intake gaskets and the TB gasket have been replaced with fel pro ones so that should also be okay.
I am just really trying to find out what is making that sound cause its some what annoying. Any ideas would be greatly appreciated.

 

Completely normal, it's the IAC whistling. Every TPI car does it. It becomes especially noticeable once you gut the airboxes.

 

thanks Ed, once again you solved a problem :hail: