Why did you replace the thermostat with a one that opens at a high temperature in stead of a stock thermostat?
If the thermostat was the problem, replacing it with the wrong one might be your problem now.
If anyone can help you, they will need to know the specifics regarding the emission tests. Which emissions were found to be too high? Publishing the actual numbers might help.
Regarding Caddyman’s assertion that these tests are meaningless, the city of Los Angeles has improved its air quality since California enacted stricter emission standards. So has Houston, Texas. With his sweeping generalized assumptions, I am sure that won’t be enough to convince him, but his statements seem laced with self righteous indignation, so I wanted to make sure the room didn’t “fall silent.”