Yea, brown's gas electrolysers are nothing new; they've been in production numerous times since 1932, but they just don't produce enough boost in economy to justify the purchase price, and time it takes to install them, unless you are going to boost your compression ratio, and use water/alcohol injection, and even then it takes years to break even. Most don't keep their cars that long.
I know. I was just thinking about our poor fellow Freeper.