Audi=No fault code, no idea
If you mean the flap on one of the rear pipe outlets its vacuum operated. Its easily disconnected and make very little difference to the noise. Leave the vacuum pipe and unit in place, just disconnect the linkage but make sure you fix the flap in the open position.
this is my 3.2 box but its probably the same
You can see the flap linkage on the top of the left pipe. I am surprised that its heavy enough to make a sound you can hear in the car TBH ??
Last edited by paddy; 23rd April 2011 at 10:30.