A filter is NOT a filter... You change your air filter out for more reasons than just convenience.
As anyone with half a brain, and has ever seen a wrench before, knows... on an internal combustion engine, air+fuel+compression=boom. The more air you can flow through the carbs, the more fuel you can suck in. The more fuel and air = more boom. So... running pods, or the pro-flow setup, will INDEED increase power, regardless of what this guy says. HOWEVER, you have to be able to get that exhaust out of there, as fast as possible. That is where the right intake/pipe combination becomes crucial.
If you only ride in sand, or dry areas, a lot of people prefer to run pods. I run pods myself, and only ride at Glamis. If you ride near water, mud, or snow, run an airbox with the pro-flow adapter, and a k&n, or foam type, with a pre-filter. One of those setups, along with removing the air box lid, is probably the most common intake mod on the banshees.