I read an article about the group that "caught" VW.
Almost 15 years ago Caterpillar was caught doing the same thing to heavy-haul engines. Part of that settlement was the money that set up this group. Their task was a light mobile system for checking diesels "on the road".
When they first hit VW's and Audi's they thought something was wrong with their test gear, as the readings were so much higher then the allowed levels.
Then they figured out it wasn't their gear.
But these VWs and Audr's were the only firm they tested that were exceeding allowed levels by that much. Most were with-in spec