If you want a CAI, you will have to build one. For rangers there are only RAI (Ram Air Intake) systems. Main difference is CAI goes under the engine and picks up cold air traveling under the vehicle and RAI stays in the engine compartment (like in my pictures).
Now to put it in perspective from my Mustang GT, we first put a little drop in K&N filter and we felt nothing. As soon as we put in the JLT intake it let loose on me. Same with my Ranger 3.0L. When I went from stock to a MAC Performance RAI it was like the banana stuck in my tailpipe was gone! 100% on a RAI. You can either make your own with simple parts at Advanced Auto or Pepboys, buy a expensive K&N RAI that looks terrible and has the same hp as other systems, or buy a good looking intake like MAC Performance that has the same hp as the K&N.
Example: A K&N for my truck would have cost $279.99 with an uglier than stock intake tube. On the other hand, a MAC Performance intake cost $179.99 with a aluminized steel intake tube and some good hp gains! On the dyno im putting 187 hp from a stock 155 hp with just the intake and my flowmaster super 44 exhaust, and thats without a tuner so far.
Hope my ranting helps!
2003 Ford Ranger Edge 3.0L Vulcan Auto Tranny
MAC Performance Ram Air Intake
Flowmaster Super 44 w/ tailpipe before the wheel
Interior and Exterior LED w/ music interface
Ford Racing front and rear Sway Bars
Limited Slip with 4.10 gears