Wow. I've just been reading this thread with rising eyebrows.
$20.000?
That could have gotten you many things, like a more efficient car, or some courses in physics and engine design. And left change for something like this:
Max Energy Econ - Hypertech (example, not necessarily suitable for your car, many others out there on the web).
And even these will not get you 100mpg on your car.
I'm also very curious how you would get that vapor you mentioned turned into power without generating heat. Burning any fuel is an exothermic reaction, which by definition generates heat. Which gives expansion, which drives the piston.
It is down to energy balance. 1 gallon of petrol contains a certain amount of energy. You can freeze that gallon or vaporize it, it will still contain the same amount of energy.
That energy will propel a certain amount of mass, like a car, over a certain distance, given other factors like friction etcetera etcetera.
Why is it that you have blown $20000 on items from people whose stories you take as is, while you question almost everything the members on here tell you?
It's been said before: there is no magic obd2 trick box that will make a stock Marquis do a genuine 150mpg on standard petrol. And there never will be.