is it where Direct Injection comes into the picture?
there is no air throttle plate, which greatly improves efficiency, and reduces piston ‘pumping losses’
I don’t think that ‘direct injection’ = ‘no throttle plate’. That’s a function of the valve actuation. The mixture has to be controlled somehow.
If I’m getting it right, unlike “regular fuel injection”, it can go from stoichiometric into “ultra lean” under low load, so it does not need throttle at all, thus does not have it
The only gas engines without a throttle plate use variable intake valve lift to control air.