Kooks is the only one that offers a LT/Cat package that supposedly does not require a tune due to the "green" option cats. otherwise it will pop a O2 sensor code sooner or later.
without a tune though you wont get the full benefit of the upgrade though.
2013 2SS Dusk Edition
Dual Mode Exhaust CAI Inc CAI
Lethal Racing Stage IV+
PER 418ci Forged LS3