You're not going to notice any real difference with just a CAI and exhaust. Sound, yeah, but not a whole lot of power.
2 and a half inch piping is the biggest I would go on a Ranger. As Trent said, the bigger you go, the more back pressure you'll lose, which means you'll lose power.
If you want power, you can get a computer chip, and it may give you a noticeable increase, but gaining more horsepower can get expensive.