I have a 9-17 build MS75 and just about every time I'm behind someone in an ICE car I smell exhaust or whatever is coming from it? Yes I have the recirculation button on with the AC on. I do not have the Bio weapon defense but really...I have had many cars and never had this before to the extreme 90% of the time. Last night was stopped at a light with AC on and could clearly see the people in front of me smoking weed. Low and behold as soon as I followed there was the smell? OK I think I remember what it smells like I have tried turning the recirc. button on and off and no difference?? Anyone have something similar? BTW I know that once in a while you will always get extreme conditions such as smoke from a fire or rich burning ICE vehicle but I'm saying its almost always there? Its bad when the wife notices because her nose is not as sensitive as mine!!