2000 gt I recently noticed the sound of air coming from the underside of the stang towards the engine bay. I haven't jacked her up yet so I cannot pinpoint where the sound is coming from. When I'm just driving the car, the sound is not evident. I only hear it if my windows or door is open and the car is idling. It would be tough to hear when reving or driving because the exhaust masks the sound. Mechanically, the car is running great. I had one of my friends plug my exhaust while I listened and the sound did not change; it remained constant. The sound that I'm hearing almost sounds like a steam train (just not as intense). I have had a manifold leak on my old v6 mustang, and this does not sound like my v6 sounded. For one, the sound of the leak on the v6 would go away once the car warmed up. On my gt, the sound remains even when the car is at operating temperature. Plus, it's less of a clicking noise and more of a sputtering air kind of noise.