Potential exhaust leak in manifold. 3 logs The vacuum actuated exhaust valve that is fitted on the car could influence the numbers. Idle : 10 seconds valve open, 10 seconds valve in active mode, 10 seconds valve in closed mode Pull with valve open Pull with valve closed. The valve is vacuum-actuated. The vacuum source is the brake booster line (tee'd). The valve is controlled with 3 solenoids to allow the valve to be open, closed or in active mode (open on load, closed when no throttle.