BD Diesel 01-16 Chevrolet Silverado/GMC Sierra 2500/3500 HD 6.6L Exhaust Manifold KitExperience performance and durability with the enhanced Duramax exhaust manifolds, specifically designed for the 2001 2016 6. 6L Duramax engines. The BD upgraded manifolds not only remove the flow restriction found on the 2001 2006 model driver's side manifold, but they also increase overall flow on both manifolds by 5%! Crafted with precision, the BD manifolds feature robust, 65% thicker designed castings constructed from high silicon ductile iron to