I don't recommend fuel additives. Just replace the filter. While you are down there check the fuel accumulator. The accumulator is right next to the pumps and filter. There is a small hose with a clamp on the accumulator nipple. Run the car for a while to build up pressure. Shut off car and disconnect that small hose. No fuel should flow out of accumulator.
You should really have someone hook up a fuel gauge. This way the pumps, check valves, and accumulator can be checked quickly.