Hi from Phoenix AZ! Picked up a non-running 1974 Plymouth Valiant Scamp

You’re probably thinking of the air pump that was put on some engines in 1975. Chrysler’s lean burn system was introduced until 1976 and only then on the 400. In 1977 Chrysler installed it on all V8 engines.
Thanks for the update. I was thinking lean burn started in 74.