Finally! I just got my '01 back after 13 days at the BMW dealership. The car seemed to run fine but I got a fault code which said, "check engine soon." BMW North America determined that carbon had built up in the secondary air ports in the cylinder heads. They had to disassemble both cylinder heads and clean out the ports. It was major work which would have cost me $3,500 to $4,000 in labor plus parts like gaskets if the car were not still under warranty. What scares me is that this car has only got 17,000 miles on the clock! What I want to know is if anybody else on this board has experienced this carbon build up problem and if so, at what mileage? The service manager told me that BMW doesn't know why the carbon built up and that furthermore, there is no guarantee it won't happen again. This car goes out of warranty in July, and I don't fancy paying $4,000 to disassemble the motor again in another 17,000 miles of driving. The service manager himself wants to know if anybody else is having or has had this problem. Thanks for any input.