The BD-Power 1041460 Full Bore Exhaust Manifold will restore the balance to your engines exhaust flow, reduce cylinder load and reduce exhaust gas temperatures. The factory driver side exhaust manifold in your 01-10 Duramax is pinched down to allow for steering shaft clearance that isn't even required! As a result, your exhaust flow is significantly disrupted. The BD-Power Full Bore Exhaust Manifold addresses this issue by maintaining internal bore size. Made from high-silicon ductile iron, the Full Bore is a direct, bolt-in replacement for the factory manifold and is even drilled and tapped to accept the most popular EGT probes.