hi everyone

Bought myself an st170 a couple of days ago. Its just started making a funny noise, from inside the car i can only describe it as an air pumping noise, something sort of turning over and over maybe? I've tracked it down and it sounds like its coming from a silver box mounted behind the inlet manifold, there's what appears to be a cable and a wiring plug going to it. The car still drives fine. Anyone have any ideas to what it could be?

Thanks
Rich