You can learn a lot by reading poorly-written rules.

4. Exhaust systems from the cylinder head exhaust ports back may be replaced with any material with the following requirements:
a. The exhaust must exit to the rear of the driver.
b. The exhaust must comply with local noise restrictions.
c. Any high flow catalytic converter(s) are allowed. Multiple catalytic converters may be replaced by a single unit. The inlet of the single replacement converter may be located no further downstream than 6" along the piping flow path from the original exit of the final OE converter. Vehicles not equipped with a catalytic converter as original equipment are not required to have one.
With that in your rulebook, do you install a cat, or do you throw it in the trash?