You're going to find conflicting information when looking at most of any part in the aftermarket world. Some people have good results, others have poor. As stated above by others as well as myself, most guys who have experience with cold air kits tend to prefer those which are made of plastic over those made of metal due to heating incomming air issues. Generally speaking, plastic = cooler while metal = hotter. Hotter air = less o2 and therefore, less power. Cooler air = denser air, more o2, and thus more power.
I recommend doing some searches on here about cold air kits and induction kits just to see what you come up with. The choice is yours. I'm only sharing with you my opinion on cold air kits and what I know by experience.