Aftermarket Exhaust in Missouri
Replacing the exhaust system is legal in Missouri, but a muffler in good working order is required and cutouts or bypasses are prohibited.
Verified against primary sources · August 2026
What the law says
Replacing the exhaust system is legal in Missouri, but a muffler in good working order is required and cutouts or bypasses are prohibited. Removing the catalytic converter is prohibited by federal law (Clean Air Act § 203) regardless of state rules. Exhaust openings must remain closed. Only the St. Louis area requires emissions inspection.
Specific Limits
- Cutouts
- prohibited
- Muffler required
- Yes
- Catalytic converter
- removal prohibited by federal law
Exceptions & Exemptions
Must not exceed noise limits, muffler required, catalytic converter tampering prohibited under federal law, cutouts and bypasses not allowed
Frequently Asked Questions
Are aftermarket exhaust legal in Missouri?
What are the exact aftermarket exhaust limits in Missouri?
Are there exceptions for aftermarket exhaust in Missouri?
Street-legal aftermarket exhaust picks
Gear that helps you mod without a ticket in Missouri.
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