Hi, I think you mean two White, one grey and one black?
If so then the two White are your heater wires, the grey is your sensor earth (supplied by the ECU above zero) and the black is the sensor output.
Your scope therefore should be connected between the black and grey leads of the sensor. When the scope earth lead is connected to the vehicles earth the output will look as yours does, this is because of the floating earth on the sensor. What are the fuel trims doing?
Can you make the new sensor read rich and lean? (promote change)
have you smoke tested the inlet and exhaust system?
Regards Mark