Ok then, check the actuator is moving freely by pressurising it with a small pump, and watch the actuator rod, make sure it starts moving at about 0.7 ish bar, fully extended by about 0.8ish bar.
If that is right, you need to check your solenoid is opening/closing when energised
Also check the brass restrictor is still in place in the pipework between the T piece and the actuator, also check the pipes are not blocked
Check the dump valve isn't leaking by removing it and blanking the pipework, then see if the boost has increased
If all this comes up with nothing, might be worth getting the autronics checked by the mapper