Turbo and MPG...

[ynot]

If it's the original turbo it's probably pooched an time for a new one.

Almost sounds like it's got too much play an it's sticking open, if ya got C-term try monitoring the the vgt commanded an actual position going down the road see of the are even, also if you step on it watch for wild swings in the actual position vs the commanded. That may give you a hint on what's going on in there.

_vgt_actuator_position
_vgt_actuator_position_commanded

;)