I think most driving miles are steady state cruising. I think with modern wide band o2 systems 90%+ of fuel is used during closed loop operation.
Typically it requires almost full throttle to get into open loop on the 4runner. I don't know if it ever goes into OL below 3k rpms - I don't know what circumstances would cause it. I haven't seen it happen and I can't create a scenario where it will happen that I'm aware of. The other OL condition is deceleration or downshifting down hills. So.. it's pretty rare for most of us in normal use.
What you think is well noted while keeping in mind that many also think the world is flat.
The facts are that open loop fueling is based on many factors and throttle position is not really one of them. The main parameter the ECU looks at to make the decision between open and closed loop is called Load and load is not RPM dependent, so your assumption about under 3k rpms is not a reality.
Also, during deceleration and downshifting down hills, the ECU automatically shuts off the fuel injectors. This function is designed in to save fuel, and while in the deceleration mode you can see the air fuel ratio go off the chart because of the massive amounts of oxygen in the exhaust system.
Also while in the deceleration mode the Load parameter is at its lowest possible setting, and this setting is well below the threshold the ECU uses to switch between closed and open loop fueling.
I would recommend reading up on how the ECU actually functions instead of making uneducated guesses on how it functions. This would enlighten you quite a bit and also make it easier for you to follow the technical part of the conversation.
Thanks for you input though,
Quirt