Odd sound from engine compartment
 

Okay, now there's another weird thing going on. There's an odd sound coming from the general area of the throttle body. I don't really know how to describe it, but it's rhythmic and not very loud. Normal or not?

The EVAP purge solenoid valve is on the back side of the intake manifold, pretty close to the throttle body. It will click at a regular interval maybe every second or so. Use a scrap piece of hose to see if that's the sound you're talking about.

It's not the EVAP solenoid. This sound is occurring 4-5 times a second. It's kind of a fluctuating, rhythmic, muffled, raspy humming sound. That's the best way I know how to describe it.