TDCI runs extremely unevenly idle (cold + low load)

Hello, with my Mondi (12/03) TDCI the diesel runs extremely “unround” in idle. The whole car wobbles and you have the impression that the engine stops right away. However, this only occurs when the car is standing and especially clearly when the engine is still cold. If I give the right gas on the highway, then the engine runs back in idle normal for a few days and after a few days of city driving, where the engine does not get really warm, the unround idle starts again from the front . I’ve already been to the workshop. However, then the demonstration effect occurred. Engine ran round… Has anyone had similar experience that the TDCI is running extremely restless in the cold state ? (In addition, there is a slight whistle, probably at the air supply for the turbocharger ??? The part is in the middle, above, very close to the windshield. A black hose is plugged on there among other things. I assume however that this is also only a follow-up phenomenon…) e even. If the engine is warm, it runs quite round and normal. In cold condition with longer, “weak” load then the whole car shakes… For every information I am grateful !!! Thomas P.S.: I read something about defective injection nozzles. It may also be related to this. Questionably only why the engine runs round when it is warm…