They mixed gasoline with pepsi, coke, sugar, and steak sauce.

None of that was fueling the lawnwower engine.
As you know, gasoline has high vapor pressure.
As you know, gasoline vapors fuel your engine, any engine.

Wouldn't a gasoline/pepsi mix, even in 50/50 still have gasoline vapors?
You bet. Did you notice the fuel lines were in the top of the container, not the bottom with the liquid? Also, small engines like that are very simple, have no computer control, and are hence... very forgiving.

After watching the whole video, I think their computer box that comes in the kit does all the work, and they sell you the rest to justify a high price for a cheap ( $30? ) computer chip. I think all the whole system does is spoof the computer to run your car lean.

I want to spoof my FEH to run lean, since the ethanol I use makes it run rich. Does anyone see any issues with doing this long-term?
-John