Pretty much any new car sold in the US, Canada, Mexico, and most of Europe. "Western" typically refers to "countries rich/developed enough to [in this case] add emissions regulations". It's a luxury that many countries haven't gotten to yet, but is widespread in North America and Europe.

The good news is that I believe Ho Chi Minh City is about to start, so hopefully they'll have much cleaner air in a couple years.

They probably mean two stroke motorcycles.