I believe there is a vacuum-reading sender on the fuel filter bowl operating that light. If the sender is working OK, it seems to be indicating excessive restriction in the fuel system.
The normal fix is to open the fuel filter bowl by removing the cap and put in a new fuel filter. I'd wipe the bowl clean and drain it some with the supplied yellow-handled valve on the bowl. While in there, I'd use a small stick (a headless match, etc) to make sure the small screen in the port for the fuel pressure regulator is clean of debris.
After doing this, start the truck and see if any improvement is present. You can check the fuel pressure via the Schrader valve on the bowl using a simple tire pressure gauge covered with a cloth to prevent excessive fuel spray with the engine idling. It should read perhaps 35 to 50 psi at idle.