What happened to gasoline in the mid 1970s?

That's what I was afraid you were saying.
Gasoline is hydrocarbons. I think we agree here.
Those that are used in the burning process with air become CO, CO2, NOx and sometimes water.
Any HC in the exhaust are left over fuel components. Are some transformed? Wouldn't surprise me. But for most of us we call it unburned fuel since they didn't completely react with the air.

No it's not. Not until it burns or evaporates. ......but yes, we do agree.