Air filter alone won't net any noticeable gains.
At best, it will allow you to hear more intake noise, causing the placebo affect that there's more power because of the "meaner" sound when you get on it.
A filter that allows more airflow, works best in tandem with a full exhaust system.
Which, of course, will require a fuel managment system and a tune.
For the amount of gain you will achieve with simply installing a "race" filter, you're better off investing the $60 in a -1/+2 sprocket setup for a little more oomph down low.
Keep the stock paper filter, it will keep things a little cleaner (and they actually flow air quite well).
I use K and N in all my vehicles. If you are driving around on the street stick with the street filter. If it is track only then you can go to a race filter, K and N also makes a race filter. I honestly would stick with a street filter. I also feel that the K and N is better than stock. Either way it won't help you if your engine doesn't need the extra air, but it won't hurt you.