Problem with wastegate/vacuum
 

Hi, am hoping someone can help me with this one, I've taken it to a friends garage a couple of times and he has suggested perhaps the next step is replacing the turbo (would clearly prefer to avoid this)

I have a 2004 2.0d sport x type, it runs perfectly fine then all of a sudden for no reason has no power whatsoever.
Fortunately I was around the corner from friends garage when it happened once so took it to him and the wastegate was stuck open and when I take the hose off there is no vacuum.
As soon as I turn the engine off/on again the wastegate functions properly and there is a vacuum.
I can take the hose off/on again and every time the wastegate is opening and closing.
I don't know what is causing the loss of vacuum and clearly want to avoid replacing the turbo. Can a wastegate itself be changed. I have no mechanical knowledge whatsoever but am helped by google, research shows it could be solenoid? Actuator (I think) hoses?

Any help/guidance would be appreciated.

Cheers

Al