just after I bought mine xj, it would stall out after a few minutes of idle, it was kinda pulsating and had a very rough idle.
it would almost die, then bump the idle up a bit and repeat this a few times and then finally die on me.
I think I had a bad connection on one of the injectors because I wiggled them around a bit, and it has been fine since.
although the previous owner had just replaced one of the injector O-rings, so that could be it too.