Hi

Recently purchased a 08 Passat 2.0TDI 140 (CBA Engine) for re-sale. After start up it flashes the glow plug light intermittently.
Plugged it into Vag-Com which showed the following code:

009571 Turbo Boost Control Position sensor circuit
P2563-000 Implausible signal-intermittent

Checked vacuum side of actuator and it moves the rod down as normal. Checked all hoses and they are neither collapsed or leaking. Swapped control valve solenoid from another car, no difference.
Checked continuity of 3 wires feeding actuator from the socket to underneath the air-box. all ok.

Fitted a brand new Genuine VW actuator and same story.
When I plug the old actuator back in and fit the vacuum pipe after a few minutes with the car at idle the rod is moving in and out every second and the control valve solenoid is pulsating on/off. Is this normal ??

Running out of patience and time, so any help much much appreciated!

Thanks guys