Just to clarify, code 67 does not say "hey, the only possible reason this code is set is because the sensor is bad". If you read the second half of the description is states "wiring open or short" which means what is says that the wiring or connection may be bad. Yes, it could be a bad sensor itself but from my years working on cars over half the time a code related to the O2 sensor comes up it's not the actual O2 sensor that is bad. A large percentage of the time the wiring to the sensor is bad.
My next comment is while I hope you fix the problem, doing an O2 eliminator is not what I would recommend. In my personal opinion it's kinda' like saying the tire got a puncture and is flat so let's just remove it instead of fixing it. I'm not as familiar with small engines and they usually are not as sophisticated as cars, but the O2 sensor is the main feedback loop to the fuel injection and ECM that tells the engine how to run. You basically take away the ability for the ECM to adjust fuel rate to the engine based on the exhaust readings. I will be curious to see what you think about it after install. Maybe it will work great, I'm just kinda' skeptical. For any car made in the last 20 years I would say you would be crazy for deleting the O2 sensors, but maybe it will work great on this???