Hmmm K&N? Isn't that filter oiled?
Yes, but you don't have too. A lot of people use way,...too much. All you need is a light coating. On the engine dyno we tested several filters.
The less amount of robbing hp & tq was a new white paper filter.
The most was a heavy oiled filter.
In between was a lightly oiled filter.
Anyway, if used for our aquarium's air, the paper would not impede much in flow.