The stock silencers work very well, if you dont mind the noise level ive heard that the ProCircuits add some HP.
You may want to look into the H-T Racing headers, they save weight,work with stock silencers and are avail in 2 different power styles.
hey guys whats up, new member from wheaton illinois.
currently own a 520exc, which im converting to street and supermoto track days. lookin forward to being on the forum, everybody seems helpfull.