Just disconnect the downpipe off the back of the turbo and check to see if the washer is sealing properly. What happens is the shaft it is mounted to slides downwards and the washer doesnt sit in the recess properly. Its easy to spot if this is the problem when you disconnect the downpipe.

You could bypass the Amal valve temporarily to test, just run the pipe from the compressor straight to the actuator. A standard actuator will olny hold around 8 psi when fitted like this and a -31 will hold around 1 bar. If the amal valve isnt operating, I would expect you would get the same results bypassing it. If the AMAL is jammed shut like my previous one, it would overboost.

You AMAL valve should click open and closed when you connect/disconnect the terminal to it. It closes when the ignition is turned, diverting boost away from the actuator, and opens when power is cut to it, allowing pressure to the actuator.