On the Evolution muffler the bolt tightens into the outlet half and the nut is just a jam nut. Loose the nut and really tighten the bolt and tighten up the jam nut. Also if it came loose make sure you check the position of the drain slot in the baffle so it can drain accumilated oil in the muffler.
flynte
whoops...should have read whole thing......sounds like new bolt time.