I just made and installed cabin filter's for me and Joey. I used the 3M ultra allergen furnace filter. It was hard as hell to cut out and i did a crappy ass job but hey it works. I didn't notice a change in the flow of air, but i'm guessing its working right. i was only able to make two, so that sucked, but minus making the filter it was relatively an easy mod, totally worth it if you have allergies.