1995 jeep gc idle problem

I have a 1995 jeep gc When I put the jeep in reverse only the idle goes down to almost a stall an sometimes slowely picks back up. The idle only does this when the jeep has been driven and the tranny is warm. when the jeep is cold, there is no problems. Motor could be warm from idleing, reverse is fine, it is only after being driven. No other gear gives me problem. I have changed the throttle pos. sensor, air idle control valve, plugs & safety nuetral. I also cleaned the throttle body. Help.