fire breathing

hey fellas, does anyone here know how to make your exhaust shoot flames. iv herd a few different theories but nothing for sure. im not taking exhaust as in headers popin out the bottem, full exhaust. iv herd u can do it with a spark plug and propane. or sparkplug and anyhting flamable for that matter. anyone ever done this? any suggestions aprretiated. oh and will that demolish your pipes

Auto-loc sells kits for $100 a pipe. www.autoloc.com I think.