K&N are great if you like unfiltered air in your engine.
They are race filters. They allow more air. They allow more air because the holes are bigger. They are for racing.
They also require a lot of maintenance. Cleaning and re-oiling. Which no one really does properly. So they are even more useless.
How many people can feel the performance gains ? NO ONE. Because they airbox, exhaust and manifolds aren't designed for them.
How many bikes have I serviced in the last 30 years with K&N filters that have gritty mess in the intake manifolds because the K&N isn't effective. 90% of them.
Ignore the marketing and the Stickers on the back windows of Chavs cars... Ditch your pointless race filters...
They just cost more money and do a crap job.