I think that the the original engineers ASSumed that the filter could be accessed by removing the owner's manual pocket. It can't. The late '05-'07 solution with the hole and the curtain was really pretty ghetto.
I have another car (Toyota) that does have a filter, and I can't believe how dusty the car still gets inside. It is never parked or driven with the windows down, so the only incoming air has to come through the filter. Makes no sense....
+1 on those Fram charcoal filters from Amazon. That is what I am using in the Toyota.