Fuel efficiency mods

[why?]

Those are good ideas.

Also think about lowering it too, the lower the car, the less air gets under it. Lightweight wheels, pulleys, and flywheel will also help gas mileage.

Get a short ram intake before you get an exhaust. I have a K&N and it helped get a couple mpg's as long as it is not freezing out.

Blocking off all of the intakes/etc in the front as well as an air damn will help, just make some of them easily removable so you can adjust for hot days.

A good place to look for other ideas is ecomodder. Just understand they are hyper sensitive. I was perma banned after asking a few questions and positively commenting on some threads.