Mar 15, 2018 (2 years ago)
Find someone better at diagnostics!
But given the lack of codes,
Which is only a place to start looking,
And guessing here
I'd start with turbo boost control faults,
Turbo boost pressure sensor/boost control solenoid and turbo boost control arm.
You see the thing about codes is there are only codes recoded/stored when the system detects when a parameter has been read as wrong.
It's easily possible for system faults to exist if the readings are close to right.
Close enough can be not enough.
See if you have a "Bosch" diagnostic specialist near you.
Those guys are usually well trained and equipped.