Try switching to a good grade fuel... after all the $hit I did with my X5, a freak twist of fate seems to have solved my issue. I was using Gulf 92 octane fuel with no ethanol added for over a year. I trusted the gas station, no reason to beleive it was poor fuel. One day, I had no choice but to put in a tank of Sunoco Ultra 93 octane (with ethanol). Within 100 miles, the issue subsided. Since then, Sunoco fuel only, and the misfire issue has not re-occurred!

No clue why, but it resolved my issue for now.... worth a try!

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2006 X5 3.0i 6MT
2004 ///M3 Coupe 6MT
1997 ///M3 Coupe 5MT
2015 X3 2.8i xDrive