If you changed your fuel filter and the heater housing above it moved ever so slightly, and now your fuel heater is leaking; that means it is time for a new seal!
These seals are hard to come by as they are a square cut O ring and specific to this application.
For install unscrew your heater, remove the old O ring, install the new one, and reinstall the heater.
One needed per engine.
This is part number 8 in the diagram:
