Originally Posted by
reverie
Wastegate is stuck open by the sounds of it. Had same problem, took the turbo off to find the WG was slightly open, cause to this is the wastegate arm becomes un spot welded. Quick check of this is to either remove the turbo elbow or give the wastegate arm few decent taps. This will knock the sleeve back in and allows the penny door to fully close. That's all I had to do and whilst the turbo was off I had it spot welded which tbf can be done whilst still fitted to the car.