Hey, I have an 89 n/a. I tried checking the actuators by putting tape on them and driving hard for a little while, The tape hadn't ripped, it was weak tape too. Anyway, that proved they weren't working, so I took them off. The diaphragm things work fine, I can blow in them to make them move. The actuators, the ones that move the sleeves, also move easily. I thought that the connection was just jammed, and it was, but there is another problem(?). I tried feeling the end of the pressure tubes to see if air came out at high rpms and none came out. How exactly is the pressure created? Is it vacuum manipulated to create pressure? Or does the ECU do it? I just want to know where to look for a problem, like a broken hose or something.

on the series 5 it's the air pump that creates the pressure, make sure the air pump is present and the belt is adjusted properly (not slipping). I'm not sure if on the series 5 it just has an always open passage from the air pump to the actuators or if a solenoid has to open up the passage at a particular rpm via ecu though... you may want to pickup a factory service manual for your car.