"The improvement in emissions was at least an order of magnitude more
than the "dilution" would have produced. This was in the days before
"storage" catalysts that can store oxygen (part of the reason mixtures
MUST oscillate around stoich - go rich, then lean, then rich) Air
needed to be added in order for the oxidizing catalist to function
effectively. "

Wow, even I wasn't aware of that. I was aware that actually a car can be made to run better without a cat, to the point where the emissions would be about the same, that something has to keep that cat lit, but not why they did that. I thought it was just like a servo hunting and or some reason they couldn't get rid of it. But i have been out of the loop for some years now.

The bottom line is the only way to test a cat is by O2 content. They cnnot check by emissions because in a properly running car, and I mean REALLY properly, there are no emissions to convert.

The cat does not help cars the really run right, it helps cars with cumulative inaccuracies in the build. Normal production tolerances do not have to be as tight. Hell, they don't even lap the valves in anymore. That'll save you a few manhours on something with 32 valves eh ?

I still maintain that no regulation has passed without the approval of the automakers. They have lobbyists. The regs give them an excuse for highway robbery. Literally. It also makes starting a new car company much harder, thus keeping down competition. No more Tuckers !