That's the filler neck. If it's rusted and falling apart, you are probably getting rust inside the tank and/or gas may be leaking out and splashing on exhaust pipe. I believe you can replace part from Ford. I would also drop the tank (make as empty as possible, fuel weighs about 8 lbs a gallon) clean it out/replace any gaskets (on top where sending unit enters tank). While it's out you may want to change fuel pump if it's never been done before. Real good time to upgrade.