If you're sticking with the stock airbox then stay away from the K&N oiled air filters. They say you won't have problems as long as you don't oil it too much but all I did was take it out of the package and install. I was obviously overoiled from the factory because after a few weeks my MAF sensor was dirty as a result.
I've never used amsoil filters but it looks worth the money having a dry filter that is cleanable.
Here's a link to the amsoil site:
AMSOIL Ea Synthetic Nanofiber Air Filter (EaA)
