go to this place...
http://www.stungbymystangmotorsports...peed_Shop.html
cheap products for all mustangs, and "starter" kits for V6 Stangs.
You'd be better off getting a desensecharger anyways, CAI's are just nice looking with the chrome which attracts people to them.
They have a kit on there with a desensecharger and ASP underdrive pulleys for your model for 252 dollars. Then your best bet would be to get gears...
3:73's would be my choice, but others are saying 4:11's. Theres a whole topic in the V6 performance section of this site talking about the differences. Best bet...3:73's IMO if your concerned with Gas.