Truck stumbling and hesitating

Hello, Was wonder if anyone has had this issue. It happened several times so far. While crusing around 70mph the truck starts stumbling and bucking like it is going to stall then it clears up like nothing happened. I've replaced the cap,rotor,ECM rebuilt new thermostat. Noticed it happens more with the A/C on. I'm in AZ and it's starting to get pretty hot during the day. I just have a feeling it's something with the outside temp causing it. Any Ideas would be helpful. Thx Rod

You might also want to check the fuel, and air filters. It kinda sounds like a fuel filter problem to me but that symptom could be a lot of things.

I forgot I replaced the fuel filter,spark plugs and wires. thx