The Cat Back's for the LS3 doesn't come with Resonators If I'm not mistaken.
The Resonators are for L99's so It doesn't drone when the AFM kicks in. not a 100% on this tho.
I have the 16483 3" Competition
If your planning to do headers I totally recommend this cat back. But if you want a LOUD exhaust this is not the one your looking for. Corsa and the Borla ATAK are the ones on the LOUD side.