Paper. The more I read, the more I realized paper was the best for the engine's long life. And since the MAF is after the filter, we know that the ECU is still making proper mixture even if the air flow is less due to the resistance of the filter or even a dirty filter. I would like to increase airflow, but there's a whole other thread about this if you search. Maybe I'll mount twin paper filter canisters on the roof, make a Y intake pipe and duct it to the driver's side engine bay vent!