Hey mate,
Widely known issue that these engines have wastegate actuator issues. There’s been a “fix” coming from BMW for 2 years according to some UK forums. Some users have pushed BMW directly for a fix and had replacement drive belts, tensioners and cover fitted to snug up the area. It has no impact on performance, it’s just annoying. Here’s a thread for more:
https://www.babybmw.net/threads/ticking-rattle-on-acceleration.143097/