A performance cam for a car would be a performance adder. How wouldn't it be. It replaces the stock part with something that gives it more power right? A performance exhaust would free air up therefore more power. A stock exhaust would be OEM replacement I guess, if thats what you want to call it. Power Adder classes? I cannot answer that one. Not sure. This debate is .. lol.. kinda can go both ways. I am only speaking of the way it makes sense to me though.