Had a long running issue where car would randomly go into limp mode with glo plug light flashing and eventually depending on how many re-starts the engine light would appear.
Code read showed P2564 turbo position sensor fault - this is part of the actuator on the turbo and from VW was £250 for replacement actuator, it has to be calibrated on diagnostics to a certain voltage level which I couldn't find any concrete info how to do and asking around friends no one wanted to tackle it.
Obviously garages won't often install or warrant jobs with customer's supplied parts. Eventually found a VAG specialist in March, Cambs. who were happy to fit it, but understandably won't /can't warranty it.
So left it with them today and got a phone call confirming that is the fault and the actuator was giving out incorrect voltages, so they're fitting the actuator and calibrating it, carrying out basic settings tomorrow. Fingers crossed it's sorted as was a pain with having to restart it numerous times so it was out of limp mode, doing about 50mph flat out!