Interesting article here (http://www.thumpertalk.com/topic/966694-does-exhaust-baffle-removal-add-more-power-performance/page__view__findpost__p__10105161). I don't know how relevant it is to a Fazer but I'd imagine it to be true. To paraphrase the article at low revs removing the baffle could be disadvantageous but it's always better at wide open throttle.
......being an old foccer i think i perfer a smooth quiet ride......
Out , due to it firing out of the can whilst bouncing it off the limiter for the benefit of the roadside crowds coming back from Le Mans Motogp last year