Between a new and clean stock paper filter and a K&N filter into the same airbox where air flow is regulated by the same holes, there's not difference in performance.
The only advantage of the K&N is that you buy once and it last for 10 years. The paper filter after 6 month needs to be replaced.
But I don't like K&N filters because they have poor filtering abilities and the engine sucks too much dust.
I prefer foam filter, because it's performance when clean are closed to a K&N filter but with better filtering abilities of fine dust.
Lot of people think paper filters are restrictive. But it's not true. Modern paper air filter are very good in performance and perfect in filtering also the smallest dirt.
The problem is that they are not cleanable and after few months their perfomance drop dramatically and need to be changed.
After 2-3 paper filters you reach the gain with a K&N/Foam filter and with a cleanable filter you stop buying filters.
Just clean and re-oil.
