They were straining to reduce NOX emmisions, that was the really tough one to reduce, that is why compression was so low, also why they had EGR valves and retarded ignition timing, they just did not know any other way to reduce it quickly, cheaply and effectively. Now they have catalytic converters, aluminum heads, high swirl heads, EFI, variable cam timing... lots of tricks to allow more compresison once again. We can apply some of there strategies invented to reduce NOX to our old stuff and improve MPG and TQ.