1996 Chevy Truck Hesitation

My truck hesitates very bad when the engine is first started but it seems to clear up after the first couple blocks. Also once it is warm it seems to surge on acceleration and after being driven hard it will usually lose most power to the point that it has to be in second gear to maintain 60mph and the truck seems to shake. This problem can usually be eliminated by shutting it down for thirty seconds and restarting it. The truck seems to run better at full throttle but still doesn't have the power that it should. When it is cold at half throttle it makes a loud clunking noise. It has new plugs new fuel filter new fuel pump new front oxygen sensors and removed catalytic converters. It is not sending any codes so a code scanner can't help in determining the problem.