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for the tank not filling up all the way it is common for the Evaporative emission canister to be plugged up and or fuel of fuel and it needs to be replaced. It is located at the rear of the truck next to the fuel pump above the spare tire.
It is #3 in the picture below.
As far as the misfire goes what code are you getting in the computer to turn the light on? Did you replace cyl #4 fuel injector?
This sounds like all the concerns are from the evaporative emission canister. Replace it to resolve your concern.
It is located at the rear of the truck next to the fuel pump above the spare tire.
do you see the pics above?