1997 Jeep Grand Cherokee Laredo hesitation Problem?

[Steve]

I have a 1997 Jeep Grand Cherokee laredo 4x4 with the 4.0L I6. I have had this hesitation problem with it when I first start it up( hot or cold engine temp, hot or cold air temperature outside). When I go to give it gas it sticks around 1500RPM and it hesitates and sometimes backfires , if you let up on the gas it will stop and you are fine. We have replaced plugs, wires, cap and rotor, Throttle Position Sensor,and the Fuel Pump, we also cleaned out the throttle plate with MAF cleaner, but the Grand Cherokee does not have a MAF. We can not nail the problem, it is a sporadic problem and it is a safety problem. Does any one have any solutions, ideas or suggestions. Thank You