This frustration arises from the situation that there are places where there is already more poison in the air than what comes out of the tailpipe of a modern,

This frustration arises from the situation that there are places where there is already more poison in the air than what comes out of the tailpipe of a modern, warmed up petrol vehicle. Los Angeles and Beijing are two examples where I have personally seen this situation on bad days. We are at the point now where mixture control and exhaust treatment leave nothing but carbon dioxide and water being emitted from a properly running automobile. With regard to parent's assertions: 1. The intake air cleaner is to keep particles out that will damage the engine (and eventually lead to lower performance and emissions control malfunction); 2. Whatever airflow meter, or not, on an engine is for combustion control, but its performance affects emissions output; 3. Exhaust o2 sensors, for 10-25 years depending on make and model, have already been telling the control system the results of combustion on each cylinder, for every combustion; 4. The catalysts are not magic. They are meant to react with specific products of combustion; There is nothing in an automobile, nor should there be, to detect and react with things like methane and ammonia. The only time you see a dust/smog detection is in luxury models that adjust the cabin ventilation in the presence of this for comfort of the occupants. There are no adjustments happening at a rate of 8 kHz: combustion in a cylinder is not even happening at this rate.