2016 Ford Fusion Intake Manifold

P0303 means a misfire in cylinder #3. Are the spark plugs original at 122000 miles? Is so, you should replace all of them. That might fix your issue. They should have been changed at 100K. If you still have a misfire after replacing the plugs and clearing the code, I would look into replace the ignition coil on cylinder #3. You might have to remove the upper intake manifold to access the plugs. You don't need to replace the manifold, just the gaskets. You didn't state which engine you have in your Fusion. There were four options in that model year.