The BMW forums are littered with wastegate rattle post.
They have one Mickey Mouse fix,
You get a long spring and attach it to the arm then attach the other end to something on your vehicle lol
This Video isn't great but at the very beginning you can hear the sound, same as ours
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He's definitely high.
I don't usually wear my sunglasses under the truck, I may try it though.
He gets every mile out of his tires.
Do you attach the other end of the spring to the rear bumper?