[swamp rat]

Something else, there is a short rubber hose below the tank, if its getting old and rotted it can collapse and restrict fuel flow, that includes any rubber line between the tank and pump, make sure its actual fuel line that is reinforced and not non reinforced rubber hose...

Check the filter like previously mentioned, try and back flow it with some air and see if there are any fine white chards of material in it, if there is that is the pickup sock deteriorating, time to replace the pickup screen.