Any system that puts the fuel gas through the throttle body displaces some air, which is responsible for the power loss- - - - -not enough oxygen to burn the fuel efficiently at high flow rates. I participated in some liquid-propane injection research that had lots of potential, but it resulted in major icing at the intake manifold because of the refrigeration effect of vaporizing the propane in the intake manifold. It would take a water-heated injector rail, and even then, warm-up would present problems.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!