What happened to gasoline in the mid 1970s?

Mattax said
Interesting the NY Times article about 1971 cars and fuels indicates a major shift in gasoline composition (and confusion) at the time. This is several years before GM helped the Feds deside cats were essential.
Auto Makers and Oil Industry Get the Lead Out’ (Published 1970)

Yeah I think GM was the first to use air pumps. The 70 or 71 model were the first, I believe. They even put air pumps on the LS6 450HP 454 cars.....with no cats. Talk about useless dilution of the exhaust. SAME pollution, just more air. lol