I have the BVC pre filter system on order, but while waiting for it I threw on a UNI Pod Filter (UP-6300AST). (It goes on the air intake, inside the lower airbox.) The filter material is pretty dense, so I was expecting some decrease in performance, but can't perceive any! I have to say that I did leave off the red pre-filter (too bulky), and I oiled it with engine oil, not the super gooey (restrictive) filter oil that you get from UNI or Maxima. The downside of this system is that you have to disassemble the airbox to get to it, and the dirt collects on the inside of the filter (which is grey and doesn't show the dirt well). But, if you have more time than money and want a simple inexpensive airbox upgrade, this does work well.