which air filter is best?

[fasterfaster]

when you did my bike the K & N filter made 2 hp difference

True Steve ............... what I wrote should have read as, I haven't seen one as yet that gives the amount of increase in Hp that it's claimed to give.
Also to note here that your Hp gained was after bike was mapped to suit not just put in place of the stock filter.
Some bikes do gain good rewards from after market filters and some don't