People buy the freak kit cause they want to keep their bike stock looking and they want something they can buy from a place and bolt right on. I personally think that all those plastic and cheesegrater pieces are stupid looking so I have no problem with a hacked air box back to fit the filters into. As long as you dont cut the tabs off the right side, so the side cover can still be attached.
But some people like the stock look, so they build their own freak kit. I think anyone that can bend a piece of metal with a pair of pliers and a hammer can build their own, and save themselves alot of money.
When you think about it, the freak kit is 2 k&n air filters, a tool kit, and $1 worth of steel brackets.
Heres a tutorial on how to make your own.
http://mywebpages.comcast.net/dziakt/Ghetto.pdf
