My zrx has a kerker bolt on,what is the better sounding/performing exhaust for these bikes? I was told it was jetted when they did the can but not sure if I would have to re-jet if I decide to go with something different. My buddy has a DRD? something like that and it is just way too loud on his zx-9 and my other buddy has the muzzy on his ZX-11. It sounds ok. Just some input would be helpful or if my can is ok I'll just leave it on. thanx guys