Do you need to loosen that lock nut and set screw to move the lever, or is that lock nut designed so that you can adjust how far the end of that screw protrudes so that it will click into one of the 3 holes by moving the lever?
If the latter is true, I would recommend that you turn the lever to at least the middle position on a warm day, and at the "open" position on a cold day until the intake warms up a bit, then move the lever to to the "closed". As far as how long should you wait to turn the lever to the fully closed position, pay attention to how the truck responds to a solid step on the gas under load. Turn it to the closed position as soon as the cold engine bog goes away.
