The power is reduced when the exhaust valve lifts too early. The graph shows the reduced power as a result of turning the dolly screw outwards 1 turn from a flush position (red lines), and then fully out to the stop (lowest 2 lines). Turning out to the stop with a light secondary (colored Red) spring makes the power delivery more like an old school non-power valve MX bike, very pipey with less low end and a high peak power.