if i get a whisper lid and use a stock filter does it still gain power? is it worth even buying it if i dont use a k&n or something?

 

As long as your paper filter is clean, you wont see much if any difference between that and a K&N. Its when the paper filter gets dirty that its flow becomes noticeably restrictive.

The only large advantage to a K&N is that you can clean and reuse it.