I have been plaqued by the same issue. I note that until the Rpm is raised above 1400 the engine is rough and feels like its miss firing on one or more cylinders. At 1400 Rpm I can hear the turbo starting to wind up and the engine is instantly quieter and smooth.
If the ALDA is adjusted at idle, screwing it out quietens the engine but allows it to smoke. Conversely screwing it in harshens the engine and makes it rock worse. The rack damper has no effect.
The question I have for the group is:-
Can the injector pump go out of calibration at idle?