What causes my truck to cut out when it gets to normal temp?

I have a 93 Nissan D21 HB with a 2.4L engine. The truck has 200k on it and up until 3 days ago it ran great. The truck starts and idles fine. The problem is that once it gets to normal operating temp, it cuts out like it's not getting any fuel. It never dies but sputters alot until i press the gas pedal further. One example, yesterday I was in a 45 MPH zone and was in fourth gear holding speed at 45, then it cuts out like I let off the gas and maybe 5 or 6 seconds later it all of sudden gets a shot of gas and jerks. In first and second gear this process is much more fierce and rapid but only when the engine gets to operating temp. I have changed the fuel filter, plugs, wires, distributor, rotor, fuel pressure regulator and put Sea Foam through a vacuum hose to clean the fuel system. What would cause this? Can anyone help