The answer to the question of whether a 2nd gen manifold will fit a 6.7 Cummins is yes, it will. In fact, the Cummins 6.7 engines have been designed to be compatible with both 1st and 2nd generation exhaust manifolds so you don’t need to worry about any incompatibility issues when installing them on your engine. The main difference between the two generations of manifolds is that the second generation has slightly larger ports than their predecessors which helps improve airflow resulting in increased power and torque output from your engine. Additionally, they are also easier to install because they come equipped with all necessary hardware for installation whereas their predecessors require additional parts such as O-rings or gaskets for installation purposes.