Guys, I believe I have finally got this fixed. The culprit (at least for my car) is the camshaft position sensor. Yes, I've changed it (and a bunch of other stuff) and the problem persisted ... so finally I took it into a shop. The guy opened the hood, took one look at it, and said it's your "aftermarket" camshaft position sensor that is causing the problem. Initially I had a hard time believing it, but ultimately let him work on it.
Changed out the aftermarket sensor (which costed $55) and put in an OEM from BMW (which costed $116!!!) and the car runs like it just came off the assembly line!!!
Here a rule to go by, any electrical part you're replacing ... pay alittle extra and get OEM!!!
Good luck with the fix!