A month ago I experienced a problem where the engine would start losing power, then sputtering, then lurching. Then it would run fine for a few miles, then repeat. I replaced the leaky fuel pump and it ran well for about 200 miles; but now the problem is back. Fuel pump doesn't seem to be defective, but how can I tell? If it's not the pump..then what? Something in the carb? It's seeming like the gas is just getting cut off. There's no consistency with when it happens, either, other than both times it has started while on a hill, then continues no matter what level. Also, if I have a new water pump, new radiator and new thermostat, what would be other reasons that the truck still runs a little hot, and when the a/c is on, it overheats?