For a good while I was running a Cobb turbo back (bellmouth DP, metallic substrate cat & 3" SS) Sounded OK, deep rumble, but I wasn't modding just for sound. Later I added a Helix up-pipe & headers from gruppe-s so now I'm down to just one cat instead of 3 as stock. Along with vf34 & supporting fuel mods the things a beast now and sounds as wicked as it runs. Still not and don't want to be the loudest thing on the streets, but NOTHING else sounds as distinctive as this mutha. Heads rotate just to see what in the hell is making that sound like Petter on a road stage.