640d turbo actuator

[Cdaulby]

Had a fault show up over the past week or so “drivetrain malfunction” which puts the car into limp mode. Took it into the garage today and they’re diagnostics have come up with a faulty turbo actuator but cannot tell which one (as it is twin turbo).
I have to go to BMW to find this out and what part code I will need... anyone had/having this problem? What can I expect...

TIA

[Eddieslofart]

I’d be checking the vacuum hoses first.