Manifold Headers for Ford & Chevy Blazer S10 GMC Sonoma (1996-2001) 4.3LHigh Flow Stainless Steel Manifold Headers for 1996 2001 Chevrolet, GMC S Series (Blazer, S10, Sonoma) 4. 3L What it Does: Replaces the restrictive factory cast iron exhaust manifolds with high flow stainless steel tubular headers to improve exhaust scavenging and lower engine bay temperatures. The Stock GMT330 Exhaust Bottleneck The factory cast iron exhaust manifolds on the Vortec 4300 V6 are notoriously restrictive, designed primarily for mass