Hi and welcome.
Good to read that you want to try things with HHO.
First things first is safety, as i can speak from my own experience.
NEVER EVER EVER EVER PUT HHO UNDER PRESSURE IN A TANK. NEVER EVER STORE LARGE AMOUNTS OF HHO ANYWHERE.
So, now you know.
Thats the reason why we like to build a hydrogen on demand system.
Secondly, adding HHO to petrol makes sense, as we all know that the element in petrol that makes a car run are the hydrogen atoms.
So, it is better to inject the HHO into the airintake manifold .
Cheers!