There is a lot of conflicting data on the effect of installing a Cold Air Intake. If you have extra money, go for it. Don't be surprised if you don't notice any difference in performance, other than making your engine noisier.
One warning: Don't get one with an oil-whetted filter element. There is a good chance the oil will end up contaminating your intake air flow meter. They are expensive.
Not worth the money in my opinion, but I never run my engines at full throttle either.