PDM, Ganzflow, & Cobb all make pretty good cold-air intakes.

i have a PDM & it cost all of $50, it's just an aluminum tube going from the fender to the factory airbox (Ganzflow is the same but costs more money) the Cobb goes from the fender to the throttle body, costs around $250 & has an inline airfilter & is supposed to work/sound really good.