Mine did this really bad. Finally at 3k miles BMW tech decided to replace the whole exhaust for me. I had them remove the old and only hand me the brand new one, and I installed the Arrow full exhaust at that time. I sold my brand new headers for $400 shipped.
i adjusted it at the header. can you adjust it at the servo too? bike runs great and rattle only lasts a sec or 2 when its cold but it drives me crazy