Stock Cats Vs. High Flow Catalytic Converter

Catalytic converters on most production cars are not designed for high performance engines. If you start hot rodding your engine and exhaust, don't forget to upgrade your cat too, since this will be a likely bottleneck. Be sure to check your local emission laws, as sometimes it is only legal to replace a catalytic converter if it is defective or broken. This is why many exhaust companies sell "cat-back" exhaust systems, which is basically the full exhaust from the exit of the cats, to the tailpipes. A good high flow catalytic converter will have an inlet and outlet the same size as the rest of the exhaust pipes to give you maximum airflow.