I'd like to think that the HHO gas is not hydrogen. Moray B King is partially right, it is a more energized form of water (In fact I believe it to be water with two fully energized P orbitals and 2 linear SP orbitals holding the hydrogen atoms.) that is denser than air and stable at room temperature.
Making the gas is all about energizing water from the 4 SP3 hybrids (tetrahedral in shape) or the P plus three SP2 triangular shaped versions without going to the typical water vapor state. Although it can be done with water vapor.
When this version condenses it does emit an electrical (actually I believe an intense plasma) pulse that can catalyze an LTNR. On it's own, it's just a 54 degree burn, but with other chemicals, it's limited only by the depth of the nuclear reactions it can complete (they are more like a chemical burn than an atomic blast with this type of ignition). It's not tapping into some Zero Point Field that a QED has to invent to make the assumption that the basic building block of matter is a particle hold water. (Or you can call it sonoluminescence.
Consider the basic building block of all matter is in fact what it converts to when you take it apart, EM fields.
BTW, it's not an over unity reaction when you consume the very matter that is present in the condensation reaction. I know Zero is not keen on Paul Pantone, but everything about his system makes sense to creating and sustaining a plasma reaction in his iron pipe vapor cavitating system that provides turbulence, electrons, and magnetic containment along with chemicals to supply the extra energy. His system can run an engine without exhaust, it's actually horribly inefficient for a matter to energy converter, (as in all Cavitating systems, the compression is spontaneous and happens within the generator, not just the piston areas) but can react with just about anything in a vapor state.
The creation of the higher energy HHO molecules is simple chemistry, put any kind of energy into a molecular system and it will absorb the types that the orbitals can, and when they max out, will release that energy at a higher frequency. Oxygen itself does this with O2 and O3. It's got the range to make HHO, or rather HOH a reasonable option. It's a special bonus that the molecule does a state change with the energy change. This is why cavitation will dissolve titanium propellers or clean polluted water or even boil water 30% more efficiently than heating it (if you don't count the cost of atomized stainless steel).
Apparently Stan Meyer's got really good at it, in his instructional videos he claimed the gas output was independent of the power in (tap water with his tubular system pulsed DC at 40KHz and IR lasers), and he was able to actually generate the gas with a drop in water to gas system that replaced the fuel injectors. He commented that the "burnt" HOH had to be recharged by the sun before he could use it again, pointing to the truth that sunlight does energize water and increase the separation of the massive molecules in liquid form. The first step to increasing the energy in individual molecules.
So the power limitation of additional electrical drain arguments, even using gas or oil as the base fuel mixed with the gas, don't really make any sense. Increasing the orbital energy properly is the answer. Adding heat harvesters to power the electronics isn't really practical if you're using HOH, as the reactions are cooler than burning gas alone. Forcing other molecules to be atomized by the energy spark is the key to more power.
Separating and identifying you have the right gas should be pretty easy. It is "denser" (not by mass) than most molecules and will settle below other gasses. It's also highly diamagnetic, so it can be contained and accelerated with any magnetic field. Even though the gas apparently has 5-6x the power of H2 in a fuel cell, it should take less electrical energy than H2 because you aren't breaking the bonds, you're just stuffing them with energy, and just cavitating the system in sunlight will do most of that for you.
These thoughts are just from the research I've done, I have no hands on experience and would appreciate feedback.