The pressure control solenoid controls how hard the bands and clutches apply, and hold. Heavy throttle means more power, so the bands and clutches have to apply harder and hold more, light throttle, not as much pressure is applied, mainly to save fuel. Higher control pressure means the pump has to work harder, which drags more power from the engine. If the pressure is too low, ie, heavy throttle but low pressure, the bands and clutches tend to slip, which causes engine flaring on gear changes....