Thinking about what you said about your ECM, the only "misfire" it can sense is if a spark plug or injector fails to fire, right? If that's the case you could easily still have cylinders misfiring from the heavily diluted charge in the cylinder; when the exhaust gets pulled back in during overlap at idle, it creates pockets of already-burned gas within the cylinder; like EGR but not controlled. When this happens it can't ignite from the spark so on the next stroke the piston just pushes it all out; inevitably there will be unburned fuel in there because the cylinder didn't actually "fire" when it was supposed to. And all this time the injector is firing each intake stroke regardless of how much oxygen is available in the cylinder when the valves close.
I don't really get the lean readings at idle for high-overlap cams though I'm kinda stumped on that lol.