I've emailed a couple of you guys who have had this problem. Basically you hear a "rattling" sound as the RPM's go up then down at around 2k.
I had the cam tensioner changed but it made no difference. It sounds just like a loose heat shield but it's not. The noise is coming from the front of the drivers side cam cover. The other side makes the same noise (in the back) but you can barely hear it.. Any ideas ? Dealer says it's normal which I know it's not. I haven't heard any other 4.2's with this problem. BTW, it's a 40v in a 2000 A8.

thanks,
Bob

Does it idle rough?

under the drivers side valve cover in the front.

unplug the cam adjuster and see if it goes away.

I just saw this post. I have the exact same problem. really notice it at low revs (usually when I am pulling into the driveway which has a wall alongside it) Dealer wasn't able to do much about it but at least the tech heard it too.