I have posted this a number of times. I guess it gets lost amongst all the naysayers.
https://flapdoodledinghy.com/HHO_generator.html
It has an almost day-by-day log of what I discovered. My best was 30% increase. However, the car runs SO much better, I would do it even if it was break even.

And I am not the only one to show gains. There are many in here.

Boosting Works
 

Hi everybody,
This is Dan and I run a hydrogen boosting web site.

Just want to say I am glad to see more and more people getting interested in hydrogen boosting.

Boosting dose work most of the time.... Like 7 out of 10 cars and most can expect a 20-30% after installing a booster. Some will get better than that and some will have no luck at all ..... Mostly imported cars.
The correct setup is +NNNN- or +NNNNN- if you are using 12 VDC or +NNN- if you have a PWM. KOH seems to work the best for an electrolight but will make your cell draw more current.

Larger cells work better than small cells and we recommend 1/2 - 3/4 LPM of HHO for every liter of engine size.
A PWM is used to control the current to your booster like a light dimmer and will make a higher quality HHO but you can set your cell up to work without one.
The reason boosting works is it lets you burn more of the fuel that would normally be wasted. I could go on and on but I just want to say,
................. Keep on boosting....... Make a cell its fun ........Make your connections under the water line so it won't blow up and use 316 stainless steel and a bubbler. ...Good luck............... Dan .............