A4 S line Saloon 2007 2.0TD - Boost Issues

wild willy

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Hi, I hope i'm posting in the correct section.
A friend of mine drives the above car and among other issues has a boost problem. I have run vagcom which advised of an over boost issue. Whilst checking to determine the operating pressure of the actuator, it appeared to operate in reverse to one on a 1.8T... no movement with positive pressure but travel was felt when pushing the wastegate back into the actuator. Does this model operate on a vacuum rather than positive boost pressure.
If i can confirm the actuator is ok, i will as a precaution change the G31 pressure sensor and the two components that make up the N75. A local audi Master tech has previously looked at the car but has not found the cause!
Any advise would be appreciated.