An exhaust I have REALLY liked on LS1 cars that sounded great, was infact a spintech set up. It was an 02' Aniversery SS Camaro with 3" Manderal Bent pipes, to a Spintech Muffler, with the stock Center-Mouth Exhaust. Spintechs defenitly have their own unique sound to them. Second to that is a GMMG or Muflex chambered exhaust.
But generally I will suport magnaflow yet again. I have not seen or heard them on an LS1 car, and im not sure what your sound preference is. But this can be a nice daily driver exhaust. Their really isnt any drone, but it does get relativly quiet at constant highway speeds and idle. It only gets loud when you the driver gets Angry
