Best get Diagnostics on the beast!
That is the first port of call..
Going the "bull in a china shop approach" will just cost you unnecessary Coin..
However I know of a vacuum pipe that runs from the turbo to the vacuum accumulator and from there over the engine to the underside of the inlet manifold they tend to split and suck in excess air when vacuum is applied this stops the turbo variable vanes from working.
Faults listed will be 'boost pressure not met' or indeed no check engine or EML lamp at all.
The pipe will need to be replaced.
Other faults are-on the EPDW valves there are 2-one for the turbo actuator and one for exhaust gas resurculation there are tiny filters they clog up with crap which causes the valve to stick.
Then you have turbo failures-you could have a siezed variable vane.
After that your into the injector side-there could be excessive runoff from an injector. but that would cause the injector to missfire.
Also
With a torch look down the O/S of the engine, at the turbo you will see the actuator, get someone to start it up while you watch the actuator you should see the control rod move This rod should move about 20mm hold and then draw back slowly if it doesn't do this either it has a vacuum fault or the vanes have siezed.
The common places for the pipe to fray and perish are as routes over the top of the engine and down under the manifold under the plastic covers.
