A manual boost controller is a simple mechanical and pneumatic control to allow some pressure from the wastegate actuator to escape or bleed out to the atmosphere or back into the intake system. This can be as simple as a T-fitting on the boost control line near the actuator with a small bleeder screw. The screw can be turned out to varying degrees to allow air to bleed out of the system, relieving pressure on the wastegate actuator, thus increasing boost levels. These devices are popular due to their negligible cost compared to other devices that may offer the same power increase.