I have a 1998 Bf 90 that will hesitate or stall at 2200 to 2500 rpms under load. When trying to powerload on to a trailer it will always stall at 2200rpm. I have changed the water separator, fuel, deck filler with cap, checked the plugs, wires, turn the carbs to 2 1/4 turns out. At all other rpms the engine runs smooth with no sputtering, hesitations etc. I did notice the the glass fuel filter will sometimes be almost empty and at idle will start to fill up again. The bulb, which is new, often seems soft and difficult to suction fuel. Am I having a fuel starvation or clogged filter problem? Any advice will be appreciated. Ron.