The best way to increase fuel economy is to buy a smaller vehicle...
I know that isnt much of an option, FYI a cold air intake isnt going to do much, but it might help.
I would get the CAI, get a Gryphon and then get a custom tune made with economy in mind. Bill can write a tune that helps get better mileage but it is all up to your foot on how much it actually helps.
You could also save money by doing the Gott's mod and not installing the CAI. Then you wouldn't have to worry about running lean with the CAI, or needing custom tunes to fix the leanness if it occurs. Research the Gotts mod and see if you think it will work for ya, it is a lot cheaper and it does almost the same thing as most, and more than some.