Hoping you helpful chaps can ... err ... help!
Recently my 2001 A4 2.0 petrol has been experiencing varying revs when idle. The rev counter sways between 9k - 12k RPM when stationary with my left foot on the clutch, or in neutral, and my right foot nowhere near the throttle. The difference is audible, as if I was pushing/releasing the throttle.
There's also a noticeable lag when pulling away, but no engine management light or any other symptoms. Not sure if it's related but I had a coilpack go a couple of months back, which I replaced myself.
Any ideas what the cause could be? It's on 105,000 miles and recently serviced at an independent (who couldn't find a problem).