Check for vacuum at the wastegate. There should be full vacuum (or close to) at idle. If you don't have vacuum there, try swapping the wastegate and EGR transducers (they're the same) and see if you either get a code or it starts working again.

There are two paths to check on in this situation:

One, the turbo actually isn't boosting and two, the ECU isn't seeing the boost that's there and not fueling for it.

For emissions/anti-smoke purposes, the ECU will only fuel the engine beyond a certain extent until it sees about +3# of boost.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250