RossMc,

The noise I had also sounded like it was coming form the center vent. It turned out to be from the radio as I described above. You might want to check that out. Just remove the radio and see if the noise stops. Plus once the radios out you can get a good look at what's going on in that area.

One note, you will have to re-enter the code for your radio when you reinstall it, no problem though the number is with your owner's manual and the little cover that it comes in.