The mounting strap for my Aftermarket Exhaust broke the other day and I had to put the OEM muffler back on the MP3. Then road up to https://motorelic.com/ to have Sean tig weld the strap back together. (No Charge by the way, took him about 2 minutes.) Well after riding around for a day I noticed the bike had a LOT more low end torque with the OEM muffler.
OEM muffler is staying on.
Unless you are running wide open every time you get on your scooter. You are better of with an OEM muffle IMHO.