I know this thread isn't active but it seemed a good place to post my wastegate story in case it might help someone.
A couple of weeks ago I took my 08 335i at 65k miles in to a local dealership telling them I was 95% sure my wastegates were rattling. It was different than others I've seen on YouTube in that mine only rattled in gear at flat throttle around 2200 RPM. No noise at idle or by just revving the engine in neutral. First trip in (2 days) they tightened some heat shield bolts and called it fixed - it wasn't. Next trip was a week and a half in and after telling me again at 3 days they were 100% sure it wasn't wastegates, they finally concluded after placing microphones all over my engine that it was - both front and rear. They quoted me $2700 to adjust them which I knew was bs and wouldn't fix anything. They said they couldn't proceed under the extended wastegate warranty because I had no codes thrown and it was just rattling. I of course picked up my car.
That day I call another dealership about 30 miles away from the first and they said to bring it in. While I was there, the shop foreman told me that they absolutely could (and have many times) work under the settlement warranty without codes thrown. I got a call today and they confirmed they are worn out beyond adjustment and are replacing both turbos at no charge!!!
Point being is definitely do not take what one dealer says if they fight you on it. Stupid really because they missed out on a good paying warranty job. I have no idea why. I'm certainly switching all of my business to the second dealership from now on.