This plug eliminates your factory O2 sensor. The stock narrow band O2 sensor is used only for low speed closed loop adjustments. When using performance exhausts or having trouble with the sensor, it's much easier to remove it. This kit takes minutes to install. Simply unplug the sensor, insert the resistor plug into your factory harness connector. This plug would leave the stock sensor in the pipe. If using on a pipe that has a factory 12mm O2 bung, we would suggest getting the kit.