First of all, the MAF has little (if anything) to do with the turbo, they're just looking for things that MIGHT be wrong to tell you. It's used by the engine controller to actuate the EGR and a couple other little things. Feel free to explain to them how the combustion process in a diesel is constrained by the fuel and it operates in an air surplus, therefore Mass Air Flow is pretty meaningless for combustion calculations.
If you're still under warranty and don't think your EGR will choke, tell them to plug it back in, clear the codes and try diagnosing the problem again. That should at least show them that it's not the culprit.
It IS possible that the boost sensor (Also caller Manifold Air Pressure Sensor) is bad or dirty or damaged. It attaches with allen screws on the top of the intake manifold just to the side of the fuel filter head and slightly obscured by the plastic guide that snakes wires over the top of the head. It's possible that they damaged it during the course of the work (or the wiring, or just got it dirty and didn't clean it out) but the replacement shouldn't be TOO expensive. Here's some good shots of the MAP:
http://liberty.eurekaboy.com/mapsensor.htmIf it IS bad, you can get a new one and here's a place that sells it for about $100
http://www.ecstuning.com/Volkswagen-Golf_V--2.0T/Search/0281002437/ES3417/Dan
_________________

2005 Silver CRD Limited

245/75R16 GoodYear Duratracs
Fumoto drain | ProVent CCV Filter
Stanadyne FM100 filter | Cummins fuel pump
GDE Eco | SEGR | BoulderBars | FrankenLift | Frankenskids