To comment on this idea,
As science works on principals why not try this on a small scale?
Stan you have a cell hooked up to an engine already correct?
Do you have the resources/time/want to test this theory?
As you already have the setup, placing a metal (copper perhaps) tube as a section of pipe that the HHO needs to transverse through to get to your engine. Once you have a stable production/engine speed (the lower the better), apply voltage increase (in both potentials) to the tube. If the theory has benifits (voltage of a particular charge can increase the "power" output of the gas) your engine speed should increase. This would become apparent by the simple sound of the engine running. If your get to say 5kv(??) and there isn't even the slightest change then your can put the idea of HV exposure to rest. If it does work then you only need to incorporate this efficiently.