What kind of mileage are you looking for?? There are modifications that can be done to increase fuel economy. I installed headers and a cold air intake. I noted a 6-10 mile per gallon increase in fuel economy.
Maybe you should try some of the easy things before you start re-designing the duratec.
Clean all carbon out of engine
clean or get new air filter
spark plugs and wires
change oil
make sure the engine is tuned up
tire pressure is correct
