i also have the same problem and talked to two dealership who said that the waste gate rattle problem is US problem not canadian. yet again same cars but across the border accept there is a problem but here bmw is quiet.
both dealership confirmed the car has waste gate rattle problem.
here is the waste gate rattle extended warranty.
in my opinion this problem exist around and we need to get together and create a case with bmw canada.
i have contacted bmw canada via email (which is the best way for tracking responses) and they just confirmed my car is out of warranty and tried to sell me extended warranty, avoiding the issue with the waste gate rattle completely.
anyone capable of creating a case with BMW Canada? we can start collecting signatures here.