[Igovert500]

He's right, the K&N might not gain much HP on it's own, but its a basic necessity in modding...you want your engine to breathe better. So a bigger intake is a good start. Any modding guide will tell you to start with that simply because it will help with every other modification. Downpipe, intake, catback, hiflow cat/testpipe, will all allow your engine to breathe better which = more hp.
After all that, it's up to you how much hp you're wishing for. You can always turbo or supercharge it, or do engine and cam work. Also, weight reduction is the cheapest way to make your car go faster. I think it's for every 100lbs you lose, you shave a 1/10 off your 1/4mile.