Is a cat-back exhaust legal in California? And in your state?

Updated October 30, 2026.

A cat-back exhaust leaves your factory catalytic converters, oxygen sensors and OBD exactly as they are, and with a Rog valved system, valves closed, your car sounds very close to stock, on the street and at inspection. Valves open, it has the voice you chose for it. If you replace the front section too, our 200-cell sport catalytic converter keeps emissions control. Each system is built from your VIN, from a 3D scan of the chassis and of the original system, and bolts onto the original mounting points with no welding. Free technical documentation for your paperwork, a 3-year warranty and free shipping, with duties and taxes included in the price.

Your vehicle.

Choose your model: we show you its exhaust, its options and the lead time.

Make Choose a make Model Choose a model See my exhaust

Or simply enter your VIN

We check compatibility with your VIN before manufacturing.

Contents 6

1. Smog Check and state inspections: how they work.
2. The rules, in short.
3. Find the exhaust for your car.
4. Frequently asked questions.
5. Write to us.
6. Sources.

Smog Check and state inspections: how they work.

• What a cat-back changes: nothing for the catalytic converters, the oxygen sensors or the OBD. Emissions tests are usually OBD-based: the test finds your factory system in place.
• California Smog Check: the Bureau of Automotive Repair runs a visual and functional inspection of the emissions components, with an OBD check on most 2000 and newer vehicles. A cat-back touches none of them.
• Emissions tests elsewhere run statewide in some states (Connecticut, Massachusetts, New Jersey, New York) and in urban areas in others (Arizona, Colorado around Denver, Georgia around Atlanta, Illinois around Chicago, Texas in designated counties).
• Safety inspections are periodic in some states (among them New York, Pennsylvania, Virginia, Massachusetts) and absent in many others; Texas ended them for noncommercial vehicles on January 1, 2025.
• The sound: valves closed, your car rolls in sounding very close to stock. The system bolts onto the original mounting points.

The rules, in short.

Rog systems carry no certification of their own: that is a choice, because a certified system sounds almost like stock, and the valves give you both. Noise rules are set by each state. In California, Vehicle Code section 27151 sets 95 dB(A) or less, tested to the SAE standard, for a passenger car under 6,000 pounds, nonoriginal exhaust equipment included, and section 27150 asks for a muffler in constant operation with no cutout, bypass or similar device; New York (Vehicle and Traffic Law section 375) and Texas (Transportation Code section 547.604) have similar muffler rules. Valves closed, your car sounds close to stock; on the street, the officer decides.

On emissions, state and federal anti-tampering laws (California Vehicle Code section 27156, the federal Clean Air Act) target the emissions control system, which a cat-back leaves alone. For a sport catalytic converter, the rules depend on your state, and federal rules on replacement converters (EPA policy) also apply; in California, a replacement catalytic converter falls under CARB Executive Orders. The catless version is for track use only. Your state decides.

Find the exhaust for your car.

Each product page shows the system, its options and its sound; each guide explains the configuration in detail. A few examples:

• Ford Mustang GT S550 (2018-2020): the exhaust and the guide.
• Ford Mustang S650 V8: the exhaust and the guide.
• Chevrolet Corvette Stingray C8 Z51: the exhaust and the guide.
• BMW M3 / M4 G80 / G82: the exhaust and the guide.
• Toyota GR Supra A90 3.0: the exhaust and the guide.
• Honda Civic Type R FL5: the exhaust and the guide.

Your car is not on the list? All our exhausts, by brand.

Frequently asked questions.

Valves closed, is my car quiet?
Yes: valves closed, the sound stays very close to stock, on the street and at inspection, and you open the valves when you choose. Your state decides.

Will a cat-back void my factory warranty?
Under the Magnuson-Moss Warranty Act (15 U.S.C. 2302(c)) and the FTC's rule (16 CFR 700.10), a manufacturer can't make your warranty depend on using its own branded parts; it can exclude damage that an aftermarket part causes.

Does a cat-back affect Smog Check or my state's emissions test?
A cat-back leaves the catalytic converters, sensors and OBD as they are, so there is nothing new for the test to find. For a sport catalytic converter, the rules depend on your state; in California, replacement catalytic converters fall under CARB Executive Orders. The catless version is for track use only. Your state decides.

How loud can my car be?
It depends on your state: 95 dB(A) under the SAE test in California, 72 to 79 dB(A) at 50 feet in Florida depending on the speed limit, and in many states a muffler rule with no figure. Valves closed, your car stays close to stock: your state decides.

Will the system fit my car?
Yes: it is built from your VIN, from a 3D scan of the chassis and of the original system, and checked before production. It bolts onto the original mounting points with no welding, at the shop of your choice.

Does Rog provide documents?
Yes: on request, we send you the technical documentation for your system free of charge, describing your configuration. At inspection, your state decides.

Write to us.

Email us at contact@rogmotorsport.com: we reply in writing, in English, within 24 hours. For instant answers: the Rog Advisor and our FAQ.

As set out in our terms and conditions of sale, it is up to each buyer to check the rules in their state.

Sources.

1. California Vehicle Code, section 27150, accessed October 29, 2026: https://california.public.law/codes/ca_veh_code_section_27150
2. California Vehicle Code, section 27151, accessed October 29, 2026: https://california.public.law/codes/ca_veh_code_section_27151
3. California Vehicle Code, section 27156, accessed October 29, 2026: https://california.public.law/codes/ca_veh_code_section_27156
4. California Air Resources Board, "Aftermarket, Performance, and Add-on Parts" (Executive Orders), accessed October 29, 2026: https://ww2.arb.ca.gov/our-work/programs/aftermarket-performance-and-add-parts
5. California Air Resources Board, "Aftermarket Catalytic Converters", accessed October 29, 2026: https://ww2.arb.ca.gov/aftermarket-catalytic-converters
6. Bureau of Automotive Repair, Smog Check, accessed October 29, 2026: http://www.bar.ca.gov/smog-check
7. 42 U.S.C. 7522, prohibited acts (Clean Air Act), accessed October 29, 2026: https://www.law.cornell.edu/uscode/text/42/7522
8. EPA, Tampering Policy, November 23, 2020, accessed October 29, 2026: https://www.epa.gov/sites/default/files/2020-12/documents/epatamperingpolicy-enforcementpolicyonvehicleandenginetampering.pdf
9. MOTOR, "The status of vehicle state inspection", August 11, 2025, accessed October 29, 2026: https://www.motor.com/2025/08/the-status-of-vehicle-state-inspection/
10. FOX 7 Austin, "Texas won't require vehicle inspections starting Jan. 1", December 5, 2024, accessed October 29, 2026: https://www.fox7austin.com/news/texas-vehicle-inspection-2025
11. New York Vehicle and Traffic Law, section 375, accessed October 28, 2026: https://www.nysenate.gov/legislation/laws/VAT/375
12. Texas Transportation Code, section 547.604, accessed October 29, 2026: https://texas.public.law/statutes/tex._transp._code_section_547.604
13. Florida Statutes, section 316.293, accessed October 29, 2026: http://www.leg.state.fl.us/statutes/index.cfm?App_mode=Display_Statute&URL=0300-0399/0316/Sections/0316.293.html
14. 15 U.S.C. 2302, Magnuson-Moss Warranty Act, accessed October 29, 2026: https://www.law.cornell.edu/uscode/text/15/2302
15. 16 CFR 700.10, prohibited tying, accessed October 29, 2026: https://www.law.cornell.edu/cfr/text/16/700.10

The Rog team