Last fall I purchased a WideBand APSX D2. I installed it over the winter and with the motor running, it is all over the place. Flashes readings at all points if the readout. I went thru the calibration step and all went well. During trouble shooting (Engine off) I set the o2 sensor on the fender well. And it reads fine, as lean as possible. I put a fuel soaked towel on it and it goes full rich. It will do this all day if I want. It is the same with power/ground straight from the battery. Only thing I can think is the passthru I used is the same one that the tach signal wire uses? Is it possible I am getting some transient bleed? Or did I miss something else completely? All help is greatly appreciated.