Actually my strong points are the transmissions, services, some wiring, chassis and 4X4. When it comes to tuneup and driveability I ask a buddy of mine that is still working at the Ford dealership. So I will pass the question on to him and it might take over the weekend because i will be outa town but I will try to get an answer back to you soon.
The leak could be a lot of things. My first guess would be the fuel cap seal because they are the first and most used seal. You might also check out your fuel pressure regulator, it almost sounds like to me that you are dealing with a rich condition which could indicate a bad regulator. Have you pulled the plugs and checked their condition? That would tell you if you have a problem in a certain cylinder. Your fuel pump could be leaking the pressure or one of the valves on the tank or the fill and return hoses at the filler neck also. These are just a few things off the bottom of my twisted mind. I will get back to you after the weekend when I hear from my friend.