Most everything posted in this thread is spot on, so far.
The expanded gasoline vapors displace air, resulting in less power potential.
Heating the fuel/air mixture results in even more expansion and less mixture density reducing power potential even more.
In low load regimes, you can see fuel economy improvements via less throttling losses, less engine ignition lead time ( as heated fuel mixtures cause increased flame front speeds and knocking ) and the ability to run lean fuel mixtures while maintaining a quality burn.
Then, there is this:
https://www.hotrod.com/articles/hrdp...-vapor-engine/
Smokey used a turbo to bring back some of the power potential. It is amazing he got it to work as he eschewed electronics as a principle.