3050 is right on the money. Use OEM recommended plugs ONLY. BMW's are now starting to use something called Ionic Knock Control. Basically it a fancy way of using the plugs themselves to detect potential knocking in a cylinder, what this means to the rest of us is the spark plugs are now doubling as sensors and they MUST be right. Right stuff all the time every time, or else drive a chevy (I'd rather shoot myself in the head personally)