charge pressure code?

The 120408 code is usually not the root cause, service information says 120408 (“charging pressure control: switch-off / pressure build-up blocked”) So this is most likely a Vanos code, when the engine is cold at idle does it make a slight rattle sound? if so this is the problem these cars are designed to have this problem at this mileage, but you can try replacing the spark plugs ignition coils, and change the oil with a new filter and then clear the codes to see what happens. Does it have any other codes? Also, lets do a smoke test for a vacuum leak, this video can help:

https://www.youtube.com/watch?v=LRKWV4Are5c

or

https://www.youtube.com/watch?v=xN5pcM-5bso

If you can send any freeze-frame/live data you have for idle, I can narrow it down a lot more. Please go over these guides and get back to us.