2 BBl Dual Exhaust
I install custom exhaust systems and have a Washington State emission certification and will say it again, it is against Federal EPA law to remove/modify an emission part on a vehicle for on road use. The exception would be for an off road use vehicle (race car). The individual states cannot overrule a Federal EPA law, period. I just read this morning that 17 states want to make their own CO2 emission standard (California is one of these states) and the EPA said no. The EPA is the one that makes the final determination on motor vehicle emission standards. A state may request higher standards than the Federal standards but it has to be approved by the EPA.
What Thrashard340 says is true, you cannot add a second cat legally on car that was supposed to have one.
Chuck