Agree with the waste gate rattle. Dealer fixed mine, but it was a different engine. There was a bulletin on the 2008 x35 IIRC.

Also agree with the hammer and nail analogy.

Don't know why a normally aspirated 4.8 would have the same noise.

is the wastegate rattle prevalent on only 35i ? a friend just got 2012 50i and nothing on his. dealer still saying its "normal" i feel like thats their answer to everything.