Put a real boost gauge on it, if only temporarily with the hose running out from under the hood into the passenger window.
Test the actuator with a bicycle pump. It should open approx 1cm by 9psi max... It should start opening sooner (5 to 6 psi but may not initially crack open until 8 or 9 when cold). Disconnect the actuator linkage while testing the actuator and check that the waste gate armature moves relatively freely.
Next would be to make sure the vacuum line from the compressor housing to the waste gate actuator isn't rerouted or obstructed.
No a boost controller is used to INCREASE the pressure needed for the waste gate to open it cannot reduce pressure.
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