It is a PWM valve.
Pulse Width Modulation.
Modern powersupplies switch on and off with a very high frequency. This is what makes e.g. a modern switching welder a quarter of the weight of one from 30 years ago.
Think of it this way: if you switch 12V on and off fast enough on a lightbulb, you can dim it to half its brightness when you turn it on for 1/100th of a second, then off for 1/100th of a second, then on, then off, etc.
But if you turn it ON for 5/100th of a second and then off for 1/100th of a second, it will burn at near full brightness.
This valve does something similar with a vacuum. By switching a vacuum fast enough (actually switching between vacuum and environmental pressure I think), it can regulate the vacuum in the tube to the turbo between a high vacuum (= very low pressure) and environmental pressure. With this it regulates the position of the vanes in the turbo in 100's of steps.
I think you can meassure between the governor and the turbo and it should be 25mmHg at 2000rpm or so. It should be somewhere in other posts about turbo problems.
On a side note, when my 'governor' was broken (tear in the membrane inside), I did not notice any problems. I opened it up hoping to put it back together and seal it again and luckily I found the tear (or I would have screwed up a totally good governor...very little chance of putting it back together). But the new one made no difference whatsoever.
What it did do was cause severe vibration in the needle of the analog vacuum meter I had attached to see how the vacuum was holding up.