Kind of slapped together
Join Date: Jan 2010
Location: Bossier City, LA
After the injector cleaner, if that doesn't help any, I'd swap that anti-slosh board. Yes, they can fail, and since they are what actually drives the fuel gauge ...
Your OTHER choice is to grab a multi meter, and check the resistance to ground of the wire from the sending unit, or at least the voltage across it. The factory service manual has you checking the resistance to see if it's in range.
No, I don't have my book open in front of me, and my PDF version isn't reinstalled on my "new" system either, or I'd give you the wire color and the range you should see.
What you're doing with that is, if it's in the middle of the range for a tank of gas, and the gauge is full high, the problem is the anti-slosh board or the gauge (luckily, you can swap just the gauge out of a base cluster). If, however, it's at the full-tank mark, then it's the sending unit or the wiring to the sending unit bad.
There's always the possibility that the float is "stuck". I had to repair the sending unit on my Dakota pickup, and as a result of my repair, when it gets down low enough to tag the "Low Fuel" light, it tends to stick there until I refill the tank.