again disconect the 3 connectors on the pcm make sure the key is off when doing this and wait about 10-15 minutes to reset adaptive memories and reconnect o2 sensor you still may have a faulty o2 sensor but this should be done first because when the cat pluggs up it senses the fuel rich the adaptive cells try to remove fuel then when exhaust flows again pcm tries to compensate and adds too much fuel as it may not be able to meet the threshold to update the adaptive fuel cells