Ok, I do not have a vaccum leak for starters. I have had this noise now since I have rebuilt the car and it's the same noise and never gets louder or change pitch. At about 5500rpm I get a loud hissing noise that almost sounds like a turbo spooling up but I have no turbo. All I did to the tranny was put a Spec stage 4 in with it's throw out bearing. The reason I think it's coming from the tranny is because when I just rev the car, there is no sound, when the clutch is engaged, the sounds comes at about 5500rpm all the way up to redline in every gear. Any thoughts??? I am sick of hearing the noise and have looked everywhere you can imagine for a vac leak, also if it was a vac leak, the sound would increase with rpm increase, that is not the case, so I don't think it's a vac leak. Please help me, I don't know what the hell it could be. PLEASE HELP!! TIA ~Jeffo
