What happened to gasoline in the mid 1970s?

Mattax said
In general the converters hate HC. Too much will shorten their life.
I cant recall the details off the top of my head. I do recall the dual air injection systems fed the exhaust manifold while the engine was warming up. This helped continue the reduction of HC into other components before it hit the cats. Once the engine was hot, the air injection was switched to the cat.
This may have begun with the introduction of the three way cats. I think my '85 is 1st or second year for AMC using 3 ways.

I have an 86 5.0 Fox body Mustang with the air pump system intact. It pumps air to the cat I am thinking to get the cat at the required operating temp ( feed fire air) one of the reasons I bought the car is it was stock. It still gets emissions inspection in Pa which is gas cap check and visual. I think leaving it there helps with that.