Hesitation while driving

Ok, I have a 1988 Jeep Cherokee Limited 4x4 271k miles, automatic. For the last 2 years, I've had a hesitation problem at about 50mph going slightly uphill hitting some bumps sometimes, never consitant at aprox. 1700 rpm with engine warmed. This is the most info I can give about the issue, other then it feels like water in the gas or like a hick-up and it's not all the time. It also sometimes dies at stop lights when I stop for long periods of times, again, never consistant. Seems to run and idle ok, maybe a light low idle in gear(750rpm)? I've replaced EVERYTHING in the engine compartment but the engine, head, knock sensor and the ballast resisstor located on the inside drivers side front fender. Have been looking for a engine compartment wiring harness, took all the wires out of the loom and looked them over for any bad connections, none found. Was thinking maybe the ecu/ecm? Acts like a major vacuum leak die at the lights when it dies? Have new 2 part vacuum harness, new crank sensor, new tps, new idle speed sensor, new maf sensor, new egr & diverter valve, new tune-up parts(plugs, wires, cap, rotor, air, fuel), new dist, new coil, pic-up coil, new temp. Sensor, new manifold temp. Sensor, new injectors, new fuel pres. Reg, new fuel pump, new coolant sensor, new thermostate, new high output 100amp alt, new batt.(800cca), new p/s pump, new rad, new clutch fan, new harmotic bal, new pulley, new a/c cond.(R12), new rad. Hoses, new heater core, and all oil leaks fixxed (valve cover, oil pan, main seals, dist. Seal). Vehicle has not been in an accident. I'm running out of things to replace, any ideas what I'm missing here?