Administrator, Resident Tater Salad
10%. Agreed on the charcoal filter.Yes, the recirc doesn't fully close as requirements dictate how much fresh air is needed to get into the vehicle. I can't find any literature on what the current requirements is.
Only other thing I can think of is charcoal hvac filter to lessen the smell/harshness. There is no way to seal off the car completely w/o supplying/producing your own oxygen source.