Originally Posted by Weasel

That would be for lack of a better term "lifter tap". There is a recently updated service bulletin on the noise that now involves changing the HVA's for the exhaust camshaft. (Hydrolic Valve Adjusters)

It is a warranty covered repair naturally so best bet would be to schedule an apointment to get it in service when they can get you in a loaner car as it will take a couple days in the shop. I've done this job myself on an E70 and it does indeed fix the noise.