There is no point to LPG. It's only an additional fuel so you are not gaining any true economy from it and you can get the same (and more) power increase alot more safely by simply turning up the injection pump.

LPG is very risky. Preignition (detonation) can blow out the headgasket or crack a piston easily. It should also be a variable flow system rather than just on-off so that you don't inject too much too soon.