I had a leak on from my Y pipe when I first got my car and it sounded like a farting noise under there until the car warmed up... found out it was leaking at the gasket... well I went ahead and bought a new Y pipe and installed it about 2 weeks ago... my exhaust finally sounded normal until today and it was making that same fart sound under there... I believe it is the same gasket, why would this be happening? Any ideas...