You cant look after the solenoid if its fully open at idle. It is on boost you need to know! Lets say the solenoid is open on off boost and when there is comming boost, the solenoid have to close. The systen works like when there have to come more boost, the solenoid have to close, if there could be knock or something else, the solenoid have to open in a short time!
The more pressure that goes in the wastegate actuator = Less boost
If you take off the hose to the wastegate, the turbo will boost all what it can! = No pressure in the wastegate actuator!