A manual boost controller can only do so much on it's own. If the spring in the wastegate actuator is adjusted too loose,the puck could get blown open by the exhaust pressure and or the pressure allowed to act on the actuator could open it too far. Either of these will limit the amount of boost you can produce. The only way to produce more boost from this point is to tighten the adjustment on the actuator to create more force to hold the wastegate shut. No amount of adjustment of the controller will help until you do this. It's a 3 way symphony. First we adjust the actuator so that it can't open prematurely or too far,then we put pressure against the check ball in the manual boost controller to stop the boost signal from acting on the actuator until a certain boost level,then we allow some of the boost signal to bleed off via a needle valve to prevent it from acting as forcefully on the actuator to produce an even greater amount of boost. Again,every electronic boost controller does these last two things.
When you disconnected the hose from the actuator,to see how much boost you could produce,was the actuator tight or loose like it is now?