Warm air is theoretically more efficient, in theory, theory and practice are the same, in practice they aren't. Warm air works very well on carbed and TBI cars, and less well on most multipoint fuel injection systems. Because.... apart from at large throttle openings the fuel is almost never suspended as droplets in the intake air... it's squirted into the port against a closed valve, sits there, evaporates from cylinder head heat, and get sucked in as mostly vapor anyway. Now also, cooler intake air will help prevent pinging with a leaner mixture, however, it takes that heat away from the head and the combustion... wasted energy... so ideally.. in theory.. you'd set things up so it was more ping resistant, and thermally efficient, like edging the chambers and ceramic coating them or something, but the ECU doesn't have that option, it says "Oh it's pinging, better back off the timing and hose in more fuel"...
I remember The RoadWarrior..To understand who he was, you have to go back to another time..the world was powered by the black fuel & the desert sprouted great cities..Gone now, swept away..two mighty warrior tribes went to war & touched off a blaze which engulfed them all. Without fuel, they were nothing..thundering machines sputtered & stopped..Only those mobile enough to scavenge, brutal enough to pillage would survive. The gangs took over the highways, ready to wage war for a tank of juice