I have a 1996 Jeep Cherokee 4x4 4.O right hand drive, it is a postal vehicle. I had to change the muffler cause it was bad and thought that while I was at it I would change the catalytic converter. I bought new parts and installed them and noticed that there was three(3) O2 sensors, two on the catalytic converter and one on the exhaust pipe. I can not find a cat with two (2) O2 sensors on it, so I decided to just leave the one off and ever since the thing has been rough. Now after it runs for about 3-5 hours it will shut down and will not start up again until it sits for 30 mins. to an hour. Does anybody have any clue on what is going on any help would be greatly appreciated!!!!