Re: CAI newbie question.
The odds of you gain 5 mpg on a CAI are very unlikely. CAI are going to give you more performance at higher RPM. You want a tune if you are looking for a gain in mpg's on top of a CAI. The larger rubber and the lift has been what impacted your mpg's. A tune could assist with this if you are driving economically. Honestly any CAI that deletes the Resonator will work similar to the others. I like the air intakes that have the closed box, but it really isn't that necessary. If you want 20 mpg's you are probably looking at a CAI, tune, and exhaust. So probably around $1'000 for all of that.
I would look at a tuner first. There should be some good options for you.