Performance accessories are anything that is going to help improve the speed of your bike, the way it is able to ride over certain terrain and in certain conditions, as well as things designed to make the bike last longer. These parts and accessories can include items such as exhausts, fuel injection systems, mapping systems, and various engine boosters. These items are said to be good to add to a new bike versus an old one, but older bikes can be upgraded with these performance parts as well.