Back a couple of posts, usually when the fuel pump on those trucks goes bad, they just quit, they don't slowly die and if you ever need to change it, it's easier to pull the bed off than to drop the tank.
Probably just need a good tune up, ei cap,rotor,wires and plugs. Have you tried to run it with out the air filter and see what happens? maybe the cam going flat, I think that was a problem on those engines also.