was doing my 12 month maintenance plan & found that my X never had the in cabin micro filters installed . glad i was replacing them. after i was done & was driving around i noticed that they leave much to be wanted in terms of filtering. i was thinking & wondered what any engineering types thought about (or knowledgeable people =) adding carbon rocks (like the kind you put in fish tank filters) and then securing it down with a screen. would eliminate odors & help out if you drive by a sewer or a sulfur plant often =p.