My TDR is built on a 1972 VW and needed to meet requirements for same. I live in Illinois in a area subject to emission testing. For years I would have to detune it, take it in to have my tail pipe sniffed, go home and retune for driving. With the advent of computerized controls, they now just connect to the under dash connector to verify everything is working OK. If car is old enough to not have connector, they wave testing because they no longer have equipment to test. Don’t know if that helps.