Throttle body Velocity Coupler (ZDX to 3.5')Applications: K20A Throttle body K20A2 Throttle body K20A3 Throttle body K20Z1 Throttle body The K Tuned velocity coupler is made from reinforced 4 ply silicone. This unique part completely removes the step commonly found at the throttle body opening, which straightens and accelerates the intake airflow and in turn helps the engine breathe easier. Intake system design and overall airflow into an engine can be critical to making maximum power. The