I think you guys mix several things together which have nothing in common. The pollution a gasoline car emits are nitrogen oxides, sulfur dioxide and unburned fuel. Carbon dioxide is NOT a pollution.
A ULEV II car like the 4.6 emits 20 ml of nitrogen oxides per mile, which is near by nothing. Any candle or barbecue emits 100 times or 1000 times more. The European Union says the outside air should not have more than 40 micro g/m3, the German OSHA allows 3600 micro g/m3 at the workplace, 8h a day and 40 years, go figure.
Carbon dioxide doesn't alter the air quality. It is 0.04% (400 ppm) in the air, these 0.04% CO2 absorbs 98% of the infrared (IR) frequency in the CO2 range. If we double or triple the CO2 concentration only 2% of more "heat" can be added. But a lot more food is added to the planet, because of increased plant growth. Every ppm CO2 added gives less heat than the ppm before.
Methane it is even less. It is 700 ppb (parts per billion) in the air AND the IR frequency is the same as the water frequency, so the heat contribution is neglectable. If we could double the concentration it would add 0.7 W/m2 heat (1366 W/m2 arrives at the atmosphere). That cow farts adds something to this is a blatant LIE.
If the sun changes the radiation of 1 W it is more than all this "man made stuff".
In Germany there is also a SMOG test but I highly doubt that they are capable to read out the myriards of engine ECUs to get to the EEPROM. They sometimes check for the P1000 error code which will be set if the car doesn't pass the internal emission checks. It will be set if you disconnect the battery and erased after several driving cycles.
PS. I'm a chemist with main subject spectroscopy.
PPS: The National Socialist put their own people first and exclude the others, the now ongoing revolution puts their own people last which is more like the communist way.