Had a similar issue with stalling and misfire. I also have a 99. Check the fuse in the panel under the hood. If its blown, it does stall and misfires. Fuse should be first row under the relays, don't know for sure which one on that row (may be the one on the left as you face the front of the car?), but it should be a 15 amps one. In my case, the wires from the o2 downstream (cat one) came loose and were shaved by the drive shaft, which caused a short and blew the fuse. Of course I found out about the damn fuse after I bought and replaced the o2 sensors...
Also, as people mentioned here, get ntk o2 sensors (napa carries them for example, 70-ish each). I bought bosh initially and they just don't work well with this engine, threw cel codes like popcorn. But from what I know, bad o2 sensors shouldn't cause engine to stall and misfire, but would make your jeep's mileage crazy low.