With clutch engaged if in neutral the truck will “rev” to 4-5000 rpm’s, and it’s not consistent. When it doesn’t it idles at 2,000 rpms.

We had the clutch replaced the a week later the fuel pump went out I replaced 3 of those I replaced fuel filter cam solenoid ignition sensor it's been purged it's fuel to the rails and spark we have emptied the gas tank replaced hoses did the timing put on a new distributer cap and rotor new battery I'm out of ideas