Found a neat write up that uses voltage at the test port. #2 & #3 pins. Voltage should read around 12.3/12.3 apparently. Higher voltage (13v)=rich and lower=lean. This is with O2 unplugged, engine up to temp.

Anyone ever try this method? I have only seen it mentioned once now.

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