And I think the general consensus is (drum roll): snake oil.
So let's see, you're essentially creating H2O2 & then mixing it with your standard everyday household gasoline.
Below is a small excerpt from Wikipedia on 'Brown's gas':
The energy required to generate the oxyhydrogen always exceeds the energy released by combusting it. (See Electrolysis of water:Efficiency).
Once again, the 1st & 2nd laws of Thermodynamics come into play & pretty much silence the swindler.