Maybe someone else who has more experience with this could chime in but even if the vavle was shut as far as it would go it should run best at an idle like this becuase thats where its supposed to be. Restricted exhuast makes more torque a free flowing exhuast makes more horsepower thats the point of the valve so you can have the best of both worlds. The valve will not completely block off the exhuast even at full closed.