Headers Manifold Shorty for Chevrolet Silverado 1500 (2002-2013) 4.8L 5.3L 6.0L 6.2L EnginesHigh Flow Shorty Exhaust Manifolds for 2002 2013 Chevrolet Silverado (Vortec LS GMT800 & GMT900) What It Does: Replaces the restrictive factory cast iron exhaust manifolds with high flow T304 stainless steel tubing to improve exhaust scavenging and reduce backpressure for increased volumetric efficiency. The Stock Silverado Weakness The factory cast iron manifolds on the GMT800 and GMT900 platforms are notorious for two major failure points: thermal