I have an injen cold air intake, and it's ok. I took it off some time ago because I got paranoid about hydro lock. I recently bought a reducer so I could reuse the injen filter without the piping.
The cheapest way to get an intake is to buy a filter with a 3.5 inch opening, remove the stock filter box, and clamp down your new filter onto existing intake. Bam, you're done. It being shorter than a cold air intake should make it more responsive. Plus it should breath more freely than stock.
Here is a link to a random eBay filter that should fit, but you could shop around for a cheaper/different color/different style/ prettier one if you want. I literally put in very little effort.
http://pages.ebay.com/link/?nav=item...d=330782854430