Saw this car for sale, great spec, and I'm sure your love!!
The wastegate rattle is abit worrying, especially if the BMW dealers have tried to sort it already. Maybe take it to a dealer that's done this kind work before??
And don't let them fob you off with the excuse of 'they are like that', mines done 60k and coming up to 7 years old, original turbos....No hint of any rattle, so make sure they sort it out before the warranty runs out
....So make sure they fit some new turbos on yours!!