Hi.
Very interesting following this discussion.
I got my brand new 330i M-sport Touring 6 weeks ago - and had "the sound" from the very first meter I drove my new car.
According to the biggest BMW dealer in DK - my car was almost the first car where they heard about the problem
However they admitted that they had a few more with same problem.....very untrustworthy !
Still waiting for a solution..... have not heard anything yet....