How can i deturmine both, how much gas fuel per minute going into my car, and how much gas from a tube per min

A vehicle is capable of running off of other fuels, such as propane and hydrogen. How can i find out how much gas/air mix is going into my engine per minute, and how can i find out how much gas is comming out of a tube from a device creating that gas? for the purpose of making sure the device is creating the same ammount of fuel as the car needs to run?
thing is, i am making a hydrobooster. i would like to run th car totally off of hydrogn. its been done before in other ways.