gsxr shared a method of removing the ALDA without removing the intake manifold. Basically you take a couple of 24mm wrenches and have at the jam nuts holding the ALDA to the IP. With the ALDA out of the way it's possible to get to the 2 bolts that take either a 10mm socket and a Philips screwdriver (I mean you can use either) that hold the shut-off actuator.

I'm not aware that there's anything in the shut-off actuator to adjust or service.

You can test the shut-off actuator easily with a MityVac. If it's good, check the vacuum lines to and from the key switch.

Sixto
87 300D