I had the exact same noise as yours and I fixed it by.. having the turbo replaced under warranty
same rattle that happens when the engine is slowing down/rpmās dropping. soon after that the wastegate seized 100% and I got a ānewā aka remanufactured turbo put in.
Iāve read people have success with putting nickel anti-seize on the wastegate, which is not really the problem youāre having but maybe lubricating it and soaking with penetrant could help the rattle also? not sure but just wanted to mention it.