I started hearing a low volume, high-pitched sound today. It is coming from a rubber tube coming off of the box that is located behind the fuse box (closer to the driver, when facing vehicle it is in the back right corner). Is this the change brake pads sound, or something else? It seems to be generated by the cable, which feels as though it is vibrating.

In addition, I've recently had a lot of problems with it. I've been crunched for time so I had the dealership replace the intake manifold gasket (which i'm hoping this is not related), replaced the radiator, and did a coolant flush. It has 103,000 miles

That sounds like a vacuum leak. Can you post a picture of the tube and the box you're talking about?

a picture of the tube that i think is making the noise
 

The issue has been resolved. It was a vacuum leak. I duct-taped the leak and that fixed it.