The sensor is junk. You could put it on the moon and it would still read lean. Buy a new sensor, do a clean air calibration. Don't run the engine with ratios lower than 12.0:1. Read the manufacturers mounting recommendation. Mount it in a position that is least likely to get any liquid on it.
Put a new set on before parking it for the winter.
A new "set"? Do you have 2 sensors? Did you get the same results with the new sensor(s)? I assume the wb control box has a +5v out. Are you also using a shared SIGNAL ground?
