After i put my F2 header and flex pipe on i have this sound. it sound just like an exhaust leak. But i have had many deff. people look at the car and know one can find a leak. has any body had this same thing happen to them? i didnt change my gasket. wherr then header and head meet. Could this be the problem? The exhasut might not be leaking until its under a hard load? is this something that could happen? Thanks for all help..this sound is killing me! ive been chasing it for over a week..