Holley Boost Control Solenoid 557-200 | Utilize the built in boost control programming in the HP and Dominator ECUs, to have complete control over your boost levels without additional control systems. To complete installation, Holley is offering boost control solenoids, specifically designed for use with the Holley ECUs. The solenoids can be dr4iven from any of the pulse width modulated outputs on either ECU, and are designed specifically for the boost control strategies designed within the ECU.