The Jaycar boost controller is very simple. Unlike commercially available Electronic boost controllers, the Jaycar unit is not closed loop. It is basically an electonic bleed valve which can bleed different amounts at different RPM points.
It will never check the real time boost pressure and compare it to some target value as the commercial units do.
Also, a decent solenoid, like those included in Turst, HKS, Blitz etc boost controller would add to the cost of the boost controller significantly.,