Audi Repair Questions? Ask a Mechanic for Answers ASAP
The lean condition (p0171) and the turbo underboost may be related- remove the turbo bypass valve from underneath, and check to see if it is broken internally. If it is the old style, the diaphragm tears..
I would be more worried about the crank/cam allocation fault- see if you can clear it, if it comes back. If so, then I would suspect that the timing may be off.
so if you clear the faults, all of these faults come back again?
Does it stumble when sitting at idle? Do you have a scan tool (VAG-COM?) that allows you to see measured value blocks? If so, check MVB 32 in the engine, there are two % values there.
any word on the value blocks? I'm wondering if you have a bad Mass Air Flow sensor