The 3 quitest mufflers I have ever run are;
Thrush , cheap units. They cost me about $17 a few years ago.
Hooker Aero Chambers, $50 a pop.
Summit racings @ 2-1/2 inchs. They came with the exhaust kit.
For cruiseing the quite hood, call summit. On acceleration, you'll not be disapointed.