well with two o2 sensors i think that you r screwed the second sensor is monitoring the first sensor (so to speak) to see if it is doing a good job and if you take the cat out then the ecu won't like it and set a code.
some expert with ecu's (electronic control unit's) and pcm (powertrain control module's) might be able to change the voltage on that second o2 sensor and make it work and or figure what voltage makes the ecu happy.