[AndrewJ]

Yeah, about the intake charge being pushed back into the intake manifold...
I can't imagine that being a huge issue. I mean, cars with using the Atkinson cycle don't (usually) have direct injection, so they are using the same limits we are. For example, only spraying fuel when the valves are open.

Still, I'm having a hard time convincing myself that the air sensor(s) are only going to count the air that's passing through one way (into the engine). I can't help but think it'll end up enriching the mix by "re-counting" the air that has been ejected back from the engine, and re-injecting the fuel for said amount of air.

Or, that air could just be all compressed and stored in the manifold somehow (TB closed), the MAF could be too slow, etc.