Full-Race 4 Port MAC Boost Control SolenoidFull Race 4 Port MAC Boost Control Solenoid w Full Race Bracket Our 4 port boost control solenoid valve is designed to target a clearly defined boost curve and improve boost responses, and in some cases with a soft WG spring quicker spool. The 4 port design works equally well in low boost applications and high boost. This differs from a traditional 3 port BCSV because it precisely directs pressure to the open and close ports of your wastegate