I have an '07 x5 4.8i and when I turn my air on, it sounds like it's muffled. I have asked someone about it and they said my "recirculating air flap" is not opening up all the way. I feel positive about this diagnosis but I want some other opinions on it. Also, when I want to use my heat, it only works when I turn the heat all the way to hot. If its any degree less than that, the air is cold. What could be causing this?