First of all, why the HELL did you make this thread in the Bugatti forum? I think it would do a little better in, oh, I dont know, the BMW 3 Series forum. But apart form that, a cylinder misfire is caused by the timing of the spark plug on that individual cylinder. I would say change the spark plug with a new one, such as a Bosche Platnum, Platnum 2, or Platnum 4. They all make great sparks. You could even buy 6 and not have a problem. Or you go to the dealership nad they'd replace it for free. So whatever you want to do is fine. Next time, however, post all BMW questions in the BMW forum.