Since these look pretty similiar to the Proma circuit, I'd say that the performance is going to be better than stock but not as good as with a serious performance exhaust. They have decent low and mid range but not a whole lot of high end. Would a Mamba fit on there? The Proma circuit type pipes have a much nicer sound but the Mamba gives better performance but is crazy loud and metallic sounding. I'm just assuming the Garelli pipes are similiar to Minarelli since they look very similiar. These are cool looking too.