If you've disconnected the hose that supplies a boost signal to the solenoid, then where the bloody hell is the wastegate actuator getting its boost signal? It normally gets it from the solenoid (the solenoid bleeds some of the incoming boost signal to atmosphere).
If the solenoid is getting no signal, then it can't supply any signal to the wastegate actuators. If the wastegate actuators don't get a signal, then they can't overcome the spring. If they can't overcome the spring they can't open the wastegate. If the wastegates don't open, then there is no bypass of exhaust gas around the exhaust wheel. If there is no bypass around the exhaust wheel, then the wheel just keeps going faster and faster. If the wheel goes faster, more boost is produced.