SpeedFactory Racing 4-Port Boost Control Solenoid Kit (External Wastegates Only) - 4-Port Solenoid Only - SF-01-052The SpeedFactory Racing 4 Port Boost Control Solenoid Kit allows precise boost control with a PWM (pulsewidth modulation) signal from a source (Engine Control Module or Electronic Boost Controller). This solenoid can raise the boost level as high as 6 7 times the spring pressure of the wastegate and offers very precise control at very high boost levels. The 4 Port Solenoid also allows you to use much lower wastegate spring pressures for better boost