While a 3 or 4 port boost control solenoid is the general ‘go-to’ when it comes to boost control, in the past another option has been used with some popularity sees compressed natural gas injectors (CNG injectors) used instead, as demonstrated on the Julian Godfrey built YB Cosworth of Ken Block, aka Cossie V2.
These CNG injectors ultimately perform the same function, just in a different way. Being injectors they are good at being controlled precisely and have a relatively high flow. In this setup two are used on this twin-port wastegate, one directing airflow to the top port in order to open the gate and reduce boost, and the second injector does the opposite to the bottom port, closing it and increasing boost.
While it may seem a little more complicated, this option can give a much greater range of control over the minimum and maximum boost levels when compared to a spring setup allowing rally cars like this to get higher torque outputs off the mark when the driver requests action from the noise pedal. With this setup, a YB Cosworth can see 46PSI of boost and 700lb/ft of torque from low RPM.