My gauge is not terribly accurate and it's time to add fuel at 1/4 tank. That might be part of your problem. When you hit the accelerator, the fuel runs to the back of the tank allowing air into the lines. It could also be water. You should have a water separater. If not, it's time to plumb one in. The last idea is that you might either have some fungus growth in the fuel or it may have even gelled depending on the temps you are seeing.
I would recommend (based on personal experience

) that you change out the fuel filters, add about 10 gallons of fuel on top of some good additive if you can, drain the water separator if you have one, and prime that puppy to make sure it's getting a good shot of fuel. Let it idle until you're sure any air that was in the fuel lines is out and take it out for a little joyride. Just don't wander too far from home....