1993 Toyota Camry. Smell gas fumes, no leaks seen. Gas Mileage seems low.

Filler neck can cause fuel odor but it generaly would little or no effect on fuel mileage. I would look at fuel pressure regulator first to see if it is leaking. Also would inspect fuel injectors and fuel lines closely.

You may want to check out evaporative emissions system. Start with fuel cap, check out purge valve and hoses that run from tank to canister and intake. Gas milage will go way down if leaking vapors.