Rear Rattle, engine noise, and wind noise from windshield.

[np2004]

Now with around 6000 miles on my 08 4.8i I have noticed more then ever when driving a lot of rattles over bumps almost like the rear seat isn't bolted in tight enough or as if the trunk lid is loose when I hit bumps I have verified both and they are tight. I have also noticed a strong amount of noise from the front windshield when driving even though I don't feel any kind of water leaks or drafts when on the highway even when it is not windy. The last issue I have noticed is that my 4.8i when running at 10F or less almost sounds like its struggling to stay on in the sense the engine noise even when parked with no acceleration almost makes two pitches of sound rather than the constant growl. Anyone else have these same problems and find out how to solve them? I have an oil sensor error so taking my X in and would appreciate any clues I can give the dealership.