It works and as a bonus, it's probably the most cost-effective additive out there. These guys are scientists, not hacks. Do some digging and you will see that they have done their research and testing.
As for the real world, back in 2018 Demonology got ~902 HP at the crank (assuming 12% parasitic loss: (794 RWHP/0.88)) on his stock/unmodified Demon with the race gas PCM. That's pretty impressive in my book...
You can check it out here: