K&N definitely flows the most air, it also flows the most dust. Hold it up to the light and see the pin pricks of light that stream through. They are much easier to service than foam filters, spray on some cleaner and wash it off with a water hose. dry it, re-oil with spray and install. hardly any mess. Here in Louisiana, we range from mud to fine dust in riding conditions; have never had a problem with our K&N filtered engines, although in dusty conditions we do use a filter skin.