An M54 engine with random stalling...it is dirty ICV until proven otherwise.

This was exactly happened to my 2004 X3 2.5i with 95K.
Cleaned the ICV, while there replace both rubber hoses too (BMW Genuine only, they are inexpensive).
After the ICV cleaning, the random stalling never happened again, problem solved.

I posted the trick for the "impossible screw" in Xoutpot E53 forum, basically using a pair of right-angle pliers to turn the screw etc. etc.