1999 Chevy Silverado loss of power

Recently, my truck has been starting fine, but after a short period of time gradually loses power, and begins to pop and crack upon heavy acceleration. If I turn off the key and immediately restart, it will return to full power for another short period and the cycle begins again. I continue this all day long. Since this problem started, I've replaced plugs, wires, cap, rotor, fuel filter, air filter, mass air flow sensor, ignition sensor, cats, and o2 sensors with no change in running condition.