Larry;
        I also grounded the AFM housing long ago for static reasons. I
would think all grounds should be at the same potential. For that reason
I added grounds to the right head and block to chassis.
        FWIW, I checked a spare, three wire O2 sensor. The heater circuit
is isolated from the metal body of the sensor.Hence no grounding is
attained here. Since the O2 output is less that one volt, readings could
very easily be messed up by bad grounds on the engine adding or
subtracting their voltage drops.

Drive Safely & Good Luck
Ken Lewis    <Kernersville,NC>
86 VW crewcab;60 356B Coupe
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