First, lemme school you on some Miller fallacies:
They have supercharger vanes between the heads. These are not for performance. When someone says they are supercharged, they are kinda right. It's not a performance roots, it's only there to get the gasses from the intake pistons to the exhaust combustion pistons quickly.
Mazda likes to play games with their Displacement ratings. But not as you would expect, they downplay their displacements. I'm not sure the exact figures, but the displacement is only the 3 cylinders, not including the evacuation and scavenging process.
If you can recall, Nissan sold the NAPS-Z versions of the CA-18 motors and the KE24s. It was a dual spark head design, that was really ahead of it's time. The Miller burns it's fuel within 40 degrees revolution of the crank, versus the standard 130-180 degree combustion. The NAPS-Z heads do it in 19 degrees. The only problem is that the exhaust stroke burn isn't as efficient as the Miller one. (Note how the Miller pistons are smaller in bore than the intake pistons. They have accounted for the lower hp combustions in the exhaust burn, whereas the NAPS-Z burns it's exhaust in the same chamber as the intake, resulting in a lesser burn).
Ford's E-tec is commonly described as "Ford's VTEC, but only on the exhaust valves". This is kinda true. Ford has managed to dual-ignite the combustion and exhaust strokes, but scavenges it's lost power by changing the exhaust valve timing to make the exhaust burns more efficient.
If you imagine the D16 VTEC-E motor or the Insights Kx VTEC-Ei motors, then you'll see how the ETEC ford design is perfectly suited for the application.
-> Steve
EDIT: ECOTEC. not E-Tec. The 2.3 Ford motors in Rangers and the such have the dual-ignition, though a single plug. Platinum plugs allow this, which weren't at all common in the earlier years. So while older dual-iginition systems required two plugs, two coils the new ones only need one.