Try shining a light through the media if it is a cut open filter. That shows the louvers openings well. I just did and while some louvers are almost closed most are open and there is lots of flow. Delco pf1233. Baldwin louvers made a little different but same thing, tons of open area even if some are almost closed. I took some pics but don't have time or energy now to show. On the Delco the holes that were barely open or closed were very open the other direction. That filter the bypass valve comes out so it easy to see both directions.