Longmtnman,
I'd put my money on fuel injection and engine managment computers. With newer engines that use direct injection, closed loop controls like O2 Sensors, Knock Sensors, Air Mass Sensors, etc..., and a computer to control it all, you can squeeze a lot more efficiency out of a lot leaner mix. I'm quite sure that plugging all of that onto our engines would eak out even more power and fuel economy. Of course, our engines would be more expensive and complex as well. Might happen eventually...
