Both power and mileage can be increased but not on an existing engine with bolt on accessories. Only with new technology.
I would argue that the mix was richer because it needed to be. Only those hydrocarbon molecules in the gasoline droplet that are in direct contact with oxygen get torn apart and bond to the oxygen atoms. Fuel droplets essentially burn through in layers of molecules, like an onion peeling. The time frame available to do this and make usable power is very limited.
Carburetors operate using the differential in pressure between the fuel in the float bowl and the wall of the venturi. That pressure differential is small, so the droplets are large, like squeezing a windex bottle slowly. Thus, in order to get sufficient surface area to create some power, more fuel was necessary.
Fuel injectors use a much higher pressure differential. 40 psi or more squirting through the orafice. Thus, it has a much larger surface to volume ratio, much more surface area, than the fuel through the orafice of a carburetor and it combusts faster, providing more usable power per fuel volume.
Moving the injectors to the intake ports and timing them in synch with the intake valves is even better. The fuel doesn’t have to swirl around in intake manifold plumbing and coalesce. Shooting the fuel directly into the chamber is even better.
Emissions are reduced by obtaining more complete combustion of the fuel, using more of its stored energy, preferably at the top half of the power stroke. Power is also increased by using more of the fuel’s stored energy. With the advent of the emissions technology, we’ve both improved power and reduced emissions. It doesn’t need to be a tradeoff. With advancements in valve timing, direct injection, combustion chamber design, ignition design, forced induction, and other technologies, we probably will be able to squeeze a more power out of the gas while still continuing to reduce emissions.
But I also recognize that at some point it becomes impossible or cost prohibitive to try to squeeze any more out of the fuel. At least with current technology.
In describing the combustion process I think we’re saying much the same things. We diverge on the subject of whether more power can be gained without increasing emissions. My theory is that gaining more power and reducing emissions are both results of the process of burning the fuel more completely. They’re entirely compatible. If I’m understanding correctly, you’re saying that in order to gain more power at this point we need to add more fuel and accept more emissions.
Currently we lose a lot of the fuel’s energy out the tailpipe. I’m convinced that someone will find a better way.