Warning: VERY Confusing if you look at it electrically, if you do it, just do it wire by wire and its not that bad.
That is how we did our flame throwers, it is NOT injected in any way, its just burning off the extra gas as we run rich. Also, please do this at your own risk, I'm not responsible for any problems you might have.
If you would like me to explain how it is done, using words, just let me know I will do my best. My dad spent about 30 mins explaining how it works, its not an easy concept.
I will post the How To we bought off ebay on flame throwers, we could not get it to work for us, but we paid $7 for it. You can have it free! The concept they tried was to stall the car and cause alot of gas to be in the exhaust and light it up, but we couldn't get it to work.