I have a similar setup I bought but haven't installed yet. Mine says to plumb a line from a propane bottle into the exhaust pipe upstream of the kit. The issue with that is is if you shut the thing down and you have no flame arrestors on the gas line, the flame can go back into the bottle and really ruin your day and vehicle. Old time flame thrower setups had carbs with manual chokes so they could richen up the exhaust gas for the flames.