One of the known issues with our trucks is a loose UVCH (Under Valve Cover Harness) connector. If this connector comes unplugged a little, it looks like this.
Since that plug connects the wires going to the fuel injectors, when the plug becomes loose, the injectors on that side stop working and your nice powerful V-8 Powerstroke becomes a 4 cylinder.
International (who made our motor) realized this was an issue and developed a plastic shim that slides under the locking tab to keep the tab engaged and prevent the connector from becoming loose.
Turns out a US Quarter is the correct thickness and width to act as a shim for this connector. The top of the quarter has to be ground down so the valve cover fits back on, but add a quarter to each side like this
And you've just invested 50 cents to keep your truck running well. Hence the 50 cent mod.
Also, if you pull the valve covers, then you should also re-torque your rocker arm pedestal bolts, circled in red, to 20 ft-lbs
and your lower injector hold down bolts, circled in blue, to 120 in-lbs, note that's INCH - lbs. They tend to work a little loose over time and the engine sounds much better after you tighten things up (unless you've got a tuner).