Drop in idle speed and hard to start hot ...empty filter...all symptoms of an air leak into the suction line in the tank...
Is the tank in cab ?
Does it do it more often when fuel tank level drops below a certain level?
Hook up an electric pump and route around the mechanical pump...mount the pump as close to the tank as possible...pumps push much better than pull...
Doesnt have to be an expensive one to test with...
You could always take the entire tank out of the test by setting up a temporary tank and electric pump in the bed...
I have seen these pickups split about half way down...works fine when tank is full...issues start after tank level drops below crack in pickup pipe...
