O2 Sensor WILL NOT CAUSE a misfire. All the O2 sensor does is compare oxygen content in the atmosphere to the oxygen content in your exhaust so the PCM can change fuel trims and control emissions. Do you have a mechanics stethoscope? Listen to the individual injectors while the engine is running and make sure they are all firing (you'll hear click click click consistently across all the injectors if they're ok). A clogged or non firing injector WILL cause a misfire and cause an O2 sensor code. The test light for the injector harness are called "noid" lights, unplug the injector - plug in the light, it will flash whenever the injector should fire. DO NOT USE a normal low impedance test light, even using it just once can fry the drivers in the controller. Also how old is your fuel filter? Never bad to put new filters on, a lot of times solves all kinds of problems.