got a noise on tickover on my mk7 that sounds like a duff duff. its not internal, but sounds like its air related. i had the aux belt off to see if it was the vacuum pump, but it still does it.
strangely though, on tick over the noise will stop for a few seconds, then start up again, it sounds most prominant on the top of the cam cover by the big round hole, but that could just be the acoustics messing with the sounds