I'm having a issue with boost on my 09 R56 JCW
Specifically it appears I loose vacuum to the waste gate above 14 psi as indicated my boost gauge. Will not boost above 15 where previously I fetched 21 psi. I do not get a code but 1/2 engine power light comes on. I previously replaced that vacuum valve under the intake manifold.
I'm going to check the ends of the hard line but could it a electrical malfunction to the valve itself? Any ideas greatly appreciated.

 

Get the codes read by a proper code reader. There are lots of proprietry BMW codes that do not show on cheap scanners. You need the BMW dealership code reader, or something like bavarian technic, autologic or autoenginuity to read the full factory codes. If the half engine light comes on there definitely 100% is a code logged, just your code reader can't see it. Sounds like a 2885 "boost pressure implausibility code" problem.

There are lots of things that can cause that, common ones including faulty diverter valve, vacuum problem, sensor faults, turbo or cat problems. The symptoms you are describing sound like a low level boost leak, most likely from a leaking diverter valve. However, until you get the codes you are guessing.

 

I second on the proper code reader. I got different codes than I did at the dealer. I was getting a rich code for a timing chain issue.