Don't we all wish we could get more power out of these things. You COULD try a K&N drop in air filter but I really doubt you'll see anything noticeable from it and it'd probably be a total waste of money.
Bottom Line: These things are not built for power.
Make your own short ram intake! I used 2 1/2 inch pipe that I picked up from a local tuner shop. K&N makes a filter to fit this size pipe also and Nopi carries it in stock (around $30). Dont forget to make your mass air flow meter wires longer by unwraping them from the conduit they are in. The filter is small enough to fit in front of your battery behind your driver side headlight. If you got any more questions just drop a line I will be more than glad to walk you though the details of all kinds of Rio stuff. Later!
Just bought a 02 Rio and it has full cold air intake header full high flow exhaust slotted and cross drilled rotors strut tower bar and now i just have to figure out where the precious owner got the parts for the car