dazco, Is it because the seat duct puts (pardon the pun) "english" on the air flow? Forcing the air to run around the filter rather than sucking most of the air through a limited section of the filter. Possibly indicated by the dirt patterns on the filter. Heavier concentrations on specific parts of the filter. You've mentioned filters before. I was just wondering if you noticed anything?
You mean pattern of dirt on the filter? No, i clean it regularly so it never gets a change to get dirty enough to see.