Welcome to werkz, A_Jan. I moved your thread to the E46 section of the site, which is more often visited by people with the technical knowledge you seek.
Tell us more about this problem. This will help us when trying to diagnose your problem remotely.
Does it stall while you're sitting at idle? Does it doing while you are in motion?
Automatic or manual transmission? Diesel or gasoline engine? 4-cyl or 6-cyl?
Please tell us the car's service history as it regards fuel delivery and ignition.
Also please tell us what the different people who have looked at it have tested, and what they have determined so far.
Shooting in the dark, I say maybe a clogged fuel filter or a faulty fuel pump could be the culprit. In fact, it wouldn't hurt anything to replace both (unless you recently did this -- in that case, we must look somewhere else).
Best of luck.