GMC Sierra 2500 HD Catalytic Converter - MagnaFlow - Direct Fit - `03-`06. This MagnaFlow California Grade CARB-compliant direct-fit catalytic converter is designed to replace the factory unit on 2003–2006 GMC Sierra 2500 HD vehicles, restoring emissions control and helping keep the check engine light off.

Built to replicate OE flow dynamics, this converter uses a spun-body design and precision 3D-scanned fitment to ensure proper alignment and function. The compact, low-mass construction and a single laser fusion weld reduce potential leak points while promoting thermal efficiency. Made from corrosion-resistant stainless components and supplied with OEM-style gaskets and hardware, it installs without cutting or welding when using the correct tools. This unit meets CARB requirements and is legal for sale in CARB-regulated states when the vehicle’s Executive Order (EO) and Engine Family Number (EFN) match the converter’s CARB Executive Order.

Features

• Direct-fit for 2003–2006 GMC Sierra 2500 HD (also fits compatible Silverado 2500 HD applications)
• MagnaFlow California Grade CARB-compliant design — legal in CARB states with matching EO/EFN
• Spun-body construction with single laser fusion weld to reduce leak potential
• Mandrel-like flow replication for consistent exhaust flow and factory performance
• Includes gaskets and hardware; no cutting or welding required for proper installation

If you have questions or want help confirming fitment, call us directly — we’re happy to assist. We offer installation and customization services at both of our locations in Austin, Texas and the Los Angeles, California area. 512-982-9393 (TX) | 562-981-6800 (CA). If you’re considering purchasing multiple items, contact us about shipping discounts. We install on premises at both locations.

CA Residents: WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov