OK.. here's the scoop. Engines run best when the fuel is fully atomised. ie, it's as much vapour as this guy is saying. The problem comes because these molecules of fuel are social creatures, and they clump together between the atomising device (initially a carburettor, later TBI/EFI, now MPI) and the combustion chamber.
That's why devices designed to 'swirl' the fuel both in the chamber and before it reached the chamber actually work. The idea is to prevent the fuel from re-integrating. The latest 'trick' is DFI, direct fuel injection, and very high pressure fuel rails. Again, designed to get the fuel atomised as much as possible in the combustion chamber...
Chris.....