The biggest issue with running a gasoline generator is maintaining the carburetor. Sooner or later, the jets will get clogged up with varnish from the gas, or some little particle. Taking the carbs apart and cleaning them is such a pain that an alternative is desirable. I dealt with this effectively with my two kW, five Hp genset. I just took the carb off and stuck a hose from my propane tank directly into the manifold. And it works fine, as long as I adjust the speed, if needed, by turning the valve a little. It does take a reasonable amount of propane, but no where near full blast.
I suppose the valve could be rigged up with an accelerator pedal linkage, for use with a car or truck. But there are special carbs for this already. The one I have looks like it would also be usable for HHO. It even has a couple of jets at the back for water mist injection. (Fed by the irregular holes.) I should be able to do something with this, even though manifold injection can't take advantage of the Thermally Explosive Energy from Meyer's system, or the Cold Fusion, which is where the OU really comes in. These will require spark plug type Injectors.
(http://s20.postimg.org/nfeaiz57x/HHO_Carb.jpg)