K&N filter seems to work for me.
Just ordinary everyday NGK CR9E's are plenty all right too. Paying more for platinum or iridium of fantasticum spark plugs never made sense to me.
BTW, you can buy those CR9E's at the local auto parts stores and pay about half what you pay at the bike dealerships. I just buy the 10-pak whenever I need 'em 'cause I'm doing two bikes all the time.
--Wag--