Please read the Allpar link provided further up the thread (post № 15), and the Popular Mechanics link in the Allpar article, to learn about the origin and development of the Clean Air Package. Also here's another magazine article testing a CAP-equipped '63 Dart and going into detail about the workings of the system. And this 1967 MTSC booklet describes the system a few years later, while this one from 1971 describes the evolution after a few more years.