Big concur with Sandy on the Centek Vernatone Mk II fg mufflers. My port muffler (probably original to the boat) rusted, and I replaced with the Mk II. It cost more, but it's worth every cent. Standing aft of my transom, the whisper (yes, whisper) of my port DD 6v53's exhaust at idle is barely noticeable. Vernatone's web site has a sound (decibel) curve, which convinced me that the Mk II was superior.
V/R