The PAIR system injects fresh air into the exhaust stream, thereby allowing any unburnt fuel to ignite inside the exhaust pipes. While this system does a good job at reducing hydrocarbon emissions, it also makes the exhaust system very hot. Also, once aftermarket mufflers have been installed, you can HEAR the excess fuel burning (pop...pop...pop, or someshitlikethat). The elimination of excess parts does make routing maintenance much easier as well. You should not expect to gain any performance numbers from doing this.