A post in that thread:
"Nobody here knows nothing about this exaust... Here are the facts. IT WILL pass emissions laws in all 50 states.
You do NOT remove the CAT. The CAT is what makes you 50 state emissions legal. YOU can BOLT it on with a FLANGE set up. If not YOU MUST cut the resonator and WELD then. You WILL be over 95dbs and that is ILLEGAL. You can help this by welding another resonator on, preferably one thats more of a glasspack(fiberglass) and/or use a silencer.
If you choose not it, it will be LOUD. You can get buy driving around at normal speeds with normal driving habbits without any problems. When you wail on it, you will wake up the whole world, and the cops will nab you from blocks away. If your smart and you dont wail in the worng places you will be just fine with the exhaust."