2001 Chevy Blazer 4.3l stalling and no restart

I have a Blazer that on a very hot day after driving for a while it will start to stall out, when you push on the gas it want to die out, also it will stall sometimes at a complete stop, to accelerate the process of stalling if you turn on the a/c it will do it too. It will not restart for a while until it cools way down. I have replaced the CRK position sensor, ignition coil, plugs, dist. cap and rotor, new fuel filter a couple hundred miles ago, had a coolant flush and new thermostat (does not seem to be overheating), I hooked a fuel pressure gauge up and there is adequate fuel pressure (55-60 psi) even while it starts to die out.