This exhaust manifold for the Civic / Integra B16 B18 is a 4-1 designed to allow the exhaust gasses to flow more freely from each cylinder and combine in a more efficient manner. 

This creates a reduction in cylinder back pressure and improved exhaust gas velocity. These improvements free up lost horsepower and torque. An added benefit is a more performance oriented exhaust sound.

Features a true 4-1 merge collector for more equal exhaust flow.  This manifold delivers the best peak horsepower gains while utilizing a 2 piece design.