I just realized that my blower motor is rated at 300W at full speed (higher than my two 120W radiator fans combined). This is a pretty significant draw at lower speeds around town. Removing my moderately-soiled cabin air filter seems to increase the air flow by quite a lot. If I can reduce the blower motor power by ~50% by removing the filter, or getting a high-flow cabin air filter, I figure that would result in a pretty decent gain in fuel efficiency.
This guy over at TDI forums replaced his air filter with some pantyhose over a mesh frame. I'm looking for a more traditional solution. Anybody know of any high flow cabin air filters available?