I wish I knew what to tell you. My car has been exhibiting the same type of weird idling periodically, and sometimes stalls while sitting in traffic. The dealer updated my software a few weeks ago, and the car stalled 3 times in a 2 day period afterwards. The dealer has had my car for three days this week, and of course it's behaving perfectly and hasn't thrown any fault codes. I don't buy the bad gas crap--I've had plenty of high performance cars that require premium gas and I always put in 93 oct from either BP, Shell or Exxon (usually from the same 3 stations--2 Exxons and one BP)--none of my other cars have had adverse reactions to any of these fuels. I know this motor is entirely different, but it would be ridiculous for BMW to design a motor/fuel system with such little tolerance for small deviations in premium fuels--I could understand if it were a problem with people using regular octane. I hope you have better luck than I am having getting your problem resolved
