[ChaZer]

The mechanic has shown me another clutch kit, which had a "Führungshülse" included, other than the kit fitted in my mini. They dont know either, why LuK delievered this clutch kit without this part.
That part in your link nevertheless looks exactly the same. So thats probably the part which has been missing in my clutch replacement, thus the noise stayed the same. Still I will report after they replaced this part.