sometimes it's generic recalled straight pipe exhaust. sometimes it ejects unignited fuel that ends up burning off at the tail pipe or so the owners hope. no matter where you live but especially if you live in urban areas, just be aware of these. our nbc station here in new york wnbc has been trying to bring them to the public's attention through their investigative unit. these are supposed to be illegal. installers claim they are for track use and not street use, problem is they are on the streets and with nerves on edge after mass shootings by semiautomatic gunfire, they can cause panic, they can trigger the gunshot detection devices that a lot of big city police departments have now installed in high crime areas that listen for that sound. these exhaust systems can trigger a police response say nothing of what can happen if you're caught using them on the road.