My opinion has absolutely nothing to do with marketing and at the same time I don't think K+N's get me any extra power. Not that much anyway. I am a victim of my own experience. Being a professional BMW motorcycle mechanic, I have serviced a lot of airheads. I see the stock paper filter leaving square airboxes full of dust and dirt on a very regular basis. Many, many times over I have seen K+N filters keeping square airboxes by far the cleanest of any filter I have seen used in them. That's not marketing. Personally, I have about 140,000 miles experience with them. I use them because they filter better than any other filter I have seen used as evidenced by my spotless airbox and snorkels. That just does not happen with the stock paper filters. At the very least, the box and snorkels get a lot of dust with the stock filters. People use them at the race track for the same reason I do. They work! If something worked better, they would be using it. I mention it just because there is so much internet BS about them. And yet in the real world tons of people use them. Not just young know nothing wanna be's but long time experienced winners. That isn't because of marketing. It's because they work.