i have a 1991 fox body gt convertible. one day it started making a LOUD hissing noise! had a few people come out and take a look at it. EVERYONE said it was the headers. i replaced the header (almost 800 dollars later) and the noise continues. no one seems to be able to tell me what is really wrong with my car. the noise comes from the back right side of the motor and maybe even towards the back. is sounds exactly like a PIST sound but loud. can anyone please help me.