I'm really hoping you can read this by logging on from someone else's home.. If you are then I won't keep you since you probably broke in since you have no friends.
Yes 5bhp from an improved air flow. Are you telling me that if I restricted my air flow to nothing, that I would not feel a hit in performance? If so then you're a bigger prick than you let on, and trust me I think you're a damn big prick.
If you do think that restricting the performance could lower the BHP then surely improving the air flow would increase the BHP? Or do you have different logic and physics in your world?
As for the original post - it's upto you. Don't expect improved performance for nothing. Depending on how you fit it, and what it replaces I reckon the K&N can make a difference. You do have to keep up with the maintenance though. Keep it clean, keep it cool.