You can't unplug them because they need power to work, but you should be able to stick the probes in the back of the sensor. You should have 4 wire O2 sensors, 2 wires correspond with the heater the other two are for the sensor. 20V is going to be too high, more than likely it's going to be in the range of 0-5V.

 

so i just bought a cat today... Magnaflow hi-flow obdII sloved thew problem as far as i can tell