Re: Wideband O2 sensor
look on eBay for Bosch LSU, they are $50 new. If the K series uses a wide band, that may work. I believe the Civic HX in the EK had a stock wide band.
As the sensors are used, they very gradually become lazier and they won't appear worn out until they are very very worn out. Basically, spend a few bucks more to get a new sensor to protect your expensive investment. No reason to cheap out on engine management.