I've always liked to think of this truck as a tractor engine with A/C (IIRC, it was either one of the Patterson brothers who said this or Brian MacGyver....forgot whom at this point).
While this discussion is technically interesting, we do not have enough information from Toyota themselves to really know what they were thinking when they designed the 1FZ-FE. It would be very interesting to be able to find one of the original 1FZ-FE engineers and talk to them about the history and development of the 1FZ. The ECU's are not changeable, so that really hinders our ability to understand and mess with ignition, fuel control systems, etc.
It is my belief that you could put the crappiest petrol you can find in the world in this engine and it will continue to putt-putt-putt along...heck, I wouldn't be surprised if you could piss in this thing and make it go....
-o-