Over the past 2 weeks i'd say, I've noticed a strange noise coming from the engine of my b5 s4. I'd say it sounds like a whirring noise. Its only audible around the 1k-2k rpm range and when I'm in a low gear or neutral. When I popped the hood and listened to the engine it sounded like the noise was coming from the left diverter valve and I heard a faint rattling as well.

My plan was to replace the diverter valves this weekend myself unless someone here thinks there might be a larger issue. Any help would be really appreciated!

Also I made a video of the noise here: