This is an idi naturally aspirated motor so it has a butterfly valve that works in conjunction with the injection pump.. So the less vacuum it sees the more diesel it injects,, to a point.. The engine rpm also increases the amount of fuel injected I just want the injection pump to act like a distributor or just the ignition source and have the propane fuel the motor to higher rpms. There is also a rack on the fuel pump that controls how much fuel will be allowed to pass through the pump and it is attached to the throttle linkage,, I guess I will start with unhooking that linkage and plugging the vacuum lines to see if that will work.. I've been looking at impco's website for one barrel propane hats but they only give part numbers. I know they make all different sizes I just don't know how to find out which one will be the same size as my throttle body