Sorry to hear that, i had the same type of problem . . . . My X5 is at the dealership now, was told there were 62 cars ahead of me with the same problem. It will be a week till I get my car back!!

Here is a thread from a few days ago: http://www.xoutpost.com/x5-e53-forum/26667-x5-blowing-out-smoke.html

Meanwhile, my beater (94' accord) rides like a soldier, sometimes I wonder why we put ourselves through these headaches!!!