Hence the dial thing in some cars or the plug in resistor in the later W126. I took my resistor out which was pulling 6 degrees. Gained some power but it will ping under heavy load. Gas milage went up a little too. They have racing fuel around here, but its leaded which is very bad for the cats!

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car