The Killer B Motorsport High Performance Oil Control Valve keeps oil from flowing out of the head breather ports while under high cornering loads. When oil is allowed to flow out of the head ports, oil level in the sump can drop, causing starvation.
The Subaru boxer platform can have issues with oil surging in the heads. It can be related to the level of performance, driving style, and track conditions. This can overwhelm the PCV's A/O separator or Catch Can, causing them to fill. Filling an A/O separator or catch can causes oil pan oil levels to drop, increasing the potential for oil starvation.
The Oil Control Valve prevents oil flow out of the valve cover ports based on the lateral forces placed on the car. Under straight line acceleration, braking, and moderate cornering, the PCV vents work just as they normally would, letting blow-by gasses vent from all ports. Under severe lateral loads, the port from the surging head (facing the outside of a corner) is closed, not allowing liquid oil to leave through the breather port. The balance ports and remaining head and crankcase ports still operate as normal. This has no negative effect on the engine or engine performance, while assuring ONLY blow-by gasses exit the breather ports.