12637647 Updated Driver Side Exhaust Manifold, 2001-2016 GM 6.6L Duramax

Hi Flow left hand manifold.Bolt in factory replacement. GM has introduced a new manifold that will flow better then the original OEM unit. Reduced pinch area near steering shaft for a nearly ideal flow. Greatly increased flow characteristics over the original unit. A great alternative to higher priced after market manifolds.