What you have done with this engine is indeed a cruel thing. Last time when I was replacing a ignition coil in my Renault, I came up with an idea: what if I add a little electronic circuit which will switch off fuel injectors in some particular moments when power demand is low, for example when you've already stopped and you are waiting for a green light but you for some reasons don't want to stop the engine. I know that I will not reduce friction loses, but think about that another way: if there are only two cylinders working and they have to produce the same amount of energy (to power up engine accessories) they will be heavier loaded - so they should work more efficiently, am I right?
If I build a circuit which steals signal from gas pedal position sensor I could switch two fuel injectors quite often, for example in situations when gas pedal is pressed less than 15%.
Another think is to change which cylinders are switch off, if I do that quite often no cylinder would get colder so whole engine would be always ready for higher power demand. What do you think? I can build such a circuit