The old mechanical red rooster system I have used on a 1480 for the last dozen years,feeds propane to the intake air pipe any time the throttle is open 1_2 or more. They have a venturi metering system that matches propane injection to air flow,so the engine will not overfuel as it lugs down. With it on,diesel rattle is gone,smoke is gone,oil stays clean a long time,the extra power allows me to run 1 mph faster. Coolant temp actually goes down inspite of the power increase.