when running a pwo or a pr3, NO o2 sensors are better than just running 1. 2 o2 sensors is how it was from the factory. the o2 sensor problem will only cause a problem at less than 25% throttle as the ecu is in open loop mode and the o2 sensors create the fuel map. after 25% throttle the ecu goes into closed loop mode(i.e. runs on the base map). when running no o2 sensors the pr3/pw0 will run in closed loop all the time. If your car has sputtering problems throughout the rpm range at full throttle its not an o2 problem.