Button. Such are my automotive interests that I kinda switched off with the arrival of EFI, and digital controls on so very much. Thus I have little to no experience of EFI.
I am guessing that your system is a single point injection as opposed to an injector for each cylinder..? That being the case then it does indeed have similarities to a carb fed engine. As has been stated elsewhere many of us have felt improvements when operating our engines in cold air, perhaps with a degree of moisture mixed in..
I suspect it is the density of the air that has the possible effect of raising the compression ratio to provide the extra performance...? At high altitude the air being somewhat less dense seems likely to reduce the compression ratio and thus engine performance..?
As for the cold and hot air supply to the intake, I suspect the engine will run better on cold air, however if too cold, carb icing could be a problem, perhaps there is a similar effect in single point injection systems...?
On old carb engines there was a Summer and Winter setting on the air filter housing which operated a flap within. In Summer the flap could be manually set to close off the hot air intake from the exhaust system the operation of which opened the cool air intake to the carb. In Winter the flap performed the opposite operation..
Perhaps single point injection suffers from icing in some way also, thus the pre heating of the air you mention may be to resist such possibilities...?
Just passing the time thinking in type with ZERO expertise..
