Engine sputtering acts like it is not getting fuel

Hello, are you saying that the truck runs better with the Mass Air Flow sensor unplugged? But the problem returns when you plug it back in? If it's running better with the sensor unplugged, the engine computer will run a default fuel strategy because it can't get any reading from the Mass Air Flow sensor, so there could be a wiring issue to the sensor causing the sensor to give incorrect readings. Are there any new codes besides the random misfire code?

https://www.2carpros.com/articles/how-a-mass-air-flow-sensor-works-maf

What is it doing now? You say it was okay, but do you feel it is running at full power? It's a 5.8-liter engine, it should have a lot of power. So, times what happens is the performance declines over time and you don't really notice it so much. And if I, for example, were to jump in and take a ride I would probably notice a lack of power right away. How does the truck idle when its sitting in Park?
It sounds like it probably needs a full tune up, spark plugs, wires, fuel filter, air filter. If a new Distributor cap helped somewhat, then the rest of the ignition system really should be done. You probably want to add a fuel system cleaner with a full tank of gas as well. It's an older truck with a lot of miles, the fuel injectors are due for a cleaning too, so a fuel system additive will help with that.

You should have him pull the spark plugs out and see what condition they are in, if the truck hasn't had a tune up in a while there can be any number of components that are just plain worn out. Checking the spark plugs is a good place to start, it sounds like there are multiple cylinders misfiring and if it's running that bad, it's possible that the Catalytic Converter will be damaged by the misfiring cylinders. When a misfire happens there is unburned fuel and air exiting the cylinder into the exhaust, that unburned fuel can cause the Catalytic Converter to overheat and melt the down, causing it to clog up the exhaust, at that point you can put the pedal to the floor and the truck will barely get out of its own way. With serious hesitation and extreme lack of power.

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

https://www.2carpros.com/articles/how-to-tune-up-a-car-engine