GM's new style exhaust manifold fits the 2001 to 2016 Duramax models. The upgraded style manifold allows better air flow and spool up throttle response compared to the original OEM unit because of the upgraded design which does not have the kink or indent like the OEM unit.
The Factory manifold that comes on the 2011-2016 LML Duramax is a replacement part and not an upgrade.

Genuine GM part is guaranteed by GM's factory warranty.