It appears that unplugging it should stop the noise so this may not be your problem. That said, I am not sure that unplugging it always eliminates the noise. I have read that you can also place your ear on the DISA while the engine is running and verify if noise is coming from it. From what I can gather, the failure points can either be a loose valve on the shaft or a failure in the vacuum system which creates the noise. Mine was a loose shaft and I don't recall any noise from it.
The system is basically a butterfly valve controlled by a shaft which is turned by vacuum actuator. While the actuator uses engine vacuum to move, it's actions are controlled electronically.
This is a good link to show how the valve is connected to the vacuum actuator.
DISA noise video.