4-2-1 Race Header for 2006-2008 Honda Civic Si, Coupe and Sedan (with High Flow Metal Core Catalytic Converter) - Produces power gains of up to 20HP vs. stock manifold. - Combine with our StreetPower cat-back exhaust system (Part #1626 for Civic Si Coupe and Part #1622 for Civic Si Sedan) for even greater power gains.- T-304 Stainless Steel- Features a huge 2 1/2" Outlet- This header includes a High Flow Metal Core Catalytic Converter.

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