I have a 2001, 5.2L, 2wd, auto/wOD, at or near 45 to 50 mph the truck coughs & loses power until I back-off. At idle it has an intermintant engine sake. I've changed out the plugs, coil, distributor cap & rotor, wires look ok. Whats its' problem? Any suggestions?

 

Post moved because it didn't belong in the DIY thread. There are tons of threads on rough running issues with these trucks. Please try doing a search for some of them.

 

check for clogged up catalytic converter. that usually prevents rev'ing the engine up beyond some amount of rpm, maybe 1500, maybe 2000, maybe 2500. you can test that in the driveway in park/neutral as it has nothing to do with gears or speed.

might be fuel pressure, fuel filter, clogged up lines. this is also sort of rpm (fuel flow) dependent.

you might want to do a compression check to rule out major (and unspeakable) malfunctions.

 

Pull codes.