Autometer A/F gauge question

Greg, the wild dancing of the gauge is due to the closed loop control of your mixture in a EFI engine.

The issue is that the sensor only has one accurate point which is at the 14.7:1 stoich ratio. The 02 sensor puts out 0-1 volt with 14.7 occuring at .5 volts. Best power ratio for most engines is aroud 12:1 and best economy is around 16:1, the O2 sensor is at it's extremes in range before those numbers are reached.