Wideband installation

Im wanting to install a wideband permanently into my 2008 wrx. Would it be possible to ditch the factory rear 02 sensor and use the sensor hole for my wideband or weld a bung into the exhaust system and keep the rear 02 sensor?

If you have removed the catalytic converter (so the sensor reads the same exhaust gas concentration as it leaves the engine) and the distance is not too close to the turbo you could do that.

You can remove the rear o2 sensor and use it to install your wideband sensor. You'll have some DTCs that will pop up so you'll need to flash the ECU with the DTCs deleted.

Just keep in mind removing the stock rear o2 can cause undesirable o2 trimming on that vehicle if not properly handled in the calibration by altering the scope of control. There are 4 tables for this if you're on a stock ECU.

This would of course be for off road use, in a country that allows for emissions defeats. You seem to be in Australia so check area laws and proceed accordingly.