I have the NTK sensor. Works great.
https://www.rockauto.com/en/moreinfo...=1180268&jsn=8
Ive heard to stay away from Bosch. Hopefully a new O2 sensor works wonders, as they really do a lot of work in measuring stuff and helping the computer make decisions on how the engine should run.
I can see my O2 sensor on my scanner doing all sorts of stuff between open loop and closed loop. The Jeep always runs in open loop until warmed up. This gives the Jeep extra fuel. This is why yours was purring when it was cold with the O2 sensor disconnected. Its when it warms up and goes into closed loop that the O2 sensor really starts working. The sensor will inform the computer how to set the air/fuel ratio.
Sounds like your basically running in open loop all the time. This is like running the Jeep with the choke on. Will run like shit!!
I think a new NTK O2 sensor for your OBD1 XJ will work wonders. Also, check the wiring around the O2 sensor, as its close to the exhaust and can melt.
Cheers,