I worked in the end of the industry where the rubber hits the road. The end user of automotive products couldn't have cared less about UHC, CO, NOX, or any other three letter substitute excuse for the performance that they used to enjoy. They didn't want technical explanations, their only interest was in 0 to 60 times, smooth idle, no stalling when you stepped on the gas and unimportant stuff like that. Zone managers, technical support people who worked for the big 3, were busy covering their exposed rear ends with fancy excuses, and left techs like me to deal with irate customers who were getting 16 to 18 mpg with their 50's and 60's cars, only to buy the 70's and 80's cars that got 9 to 12 mpg and wouldn't pull the hat off your head.
Wouldn't go back to that era for any amount of money.
Your experiences may vary a bit.
Jim Hupy