I have an '05 A3 TDI which currently has a strange droning noise when the car gets above 15/20mph. Hard to tell whilst driving whats causing it, initially I thought possibly the exhaust or breather pipes but its neither. I have recently fitted a new throttle body after the last one got sooted up and jammed, dont know if the noise is necessarily related, ie the turbo? The noise stays and gets slightly louder as the speed builds, if I drop the clutch and let the revs drop the noise remains, it only goes away (or isn't noticable) when I drop below 20mph again. Anybody any ideas?