This has all been pretty thoroughly researched, emissions testing and these other feel good measures do little to address pollution. It's been a long time since I've looked at it but while in grad school I did a couple of papers on the subject. The most effective way to curb air pollution from cars is to target the junkers spewing visible emissions. The time wasted and lost economic productivity from requiring late model cars to sit in line at an emissions testing facility is pretty monumental. I would guess vehicles with aftermarket tunes are pretty statistically insignificant when it comes to the amount of pollution they are producing. I'm all for new technology but this isn't really about curbing "green house" gases it's more about engineering social change unless you are some private jet flying elite who makes the annual pilgrimage to Davos Switzerland.