Hey man, my 98 TJ is having the same issue, it only happens during acceleration and only occasionally like once a day it will pop a backfire and only when hot. I have just swapped the throttle body with a 4.0L keeping only the original AIS, new wires, new plugs, new exhaust/intake gasket. I have a new coil, cap and rotor coming from performance distributors tomorrow. Also I have checked the computer for any error codes. If the ignition parts don't fix it I will do the fuel pressure checks and then the catalytic converter to see if it's starting to clog.