its covered in the nissan r33 service manual, you should download it and check for yourself, well worth a read
you need to get a pnuematic pressure gun thingy and attach it to the actuator, and keep building pressure slowly until the actuator rod moves
it should move around 0.70kgcm2 from memory (its in the service manual, the exact number)
if the rod doesnt move, its failed or broken / damaged etc
if the rod moves freely then your boost controller is mangled, damaged, setup wrong, adjusted incorrectly, or faulty
replace or remove and try again
its unlikely the actuator has failed, as its such as simple and old device
its likely your controller has something wrong, is setup wrong, is set too high or something else
try removing it, the car should run stock boost, around 0.70kgcm2 or +5ish on the stock guage