I have a 2003 A4 1.8T Convertible just coming up to 80,000 miles, and have an intermittent noise coming from what I can only explain as the external exhaust type area. It only happens when you turn the car over, or switch the engine off. I can best describe it as a if something is stuck and is released, like a moan type noise lasting a second at most. Anyone have any ideas what the hell this could be? It hasnt been picked up in any inspection and it was there when I bought the car about a year ago.