This is a strange problem that I can't seem to fix. When I am driving for about 45min to an hour, if i give the engine any more than 1/4 throttle it will hesitate, sputter, backfire, etc. It does not do this under the time stated above. If I turn the engine off for a few seconds then turn it back on, it runs fine for about 10-15min then it acts up all over again. I have changed the fuel filter, throttle position sensor, cap & rotor, plugs, plug wires, and O2 sensor.
Any insight anyone may have is appreciated.