1993 Toyota Pickup Cold Engine Hesitation/Stumble

I have a 1993 Toyota Pickup 22re with 155,000 miles. When trying to accelerate while engine is cold, the engine hesitates or stumbles, like it's out of gas. If I press the pedel to the floor, it takes off. This only happens until engine reaches full operating temp. If I turn the truck off and let the motor cool it does it all over again. The CEL never comes on and I don't have any codes. Gas mileage has dropped about 1.5 mpg since problem started about a month ago. The timing chain, head gasket, O2 sensor, fuel pump and cat. Convertor was replaced at 109k miles. I just replaced fuel filter, air filter, coolant temp sensor, new plugs, plug wires, coil, cap, rotor. Again, this only happens when engine is cold. After it reaches normal operating temp, truck drives perfect. Thanks for any advice!