I'm posting this in case it can help someone.

I had a rattle coming from the passenger side only when the weather was cold. It sounded like it was from the dash or from the front part of the passenger door.

I tried everything. I took apart the door and felted everything. I took apart the radio and felted everything. I even took off the side vents, glove box, knee air bag etc. I nearly took the dash off before I tried one last thing.

Turns out the problem was in the engine compartment. Some wires from the HID lights I installed were tapping the body. The sound travelled along the body panels, to the door and upper dash area. After taping up the wires the rattle went away.

Be wary of rattles and taps near your body panels. The car transfers sound amazing well into the cabin. It's good at blocking non-contact noise but not anything tapping the body.

 

Thanks for the tip! I plan on changing my halogen fog lights to the OEM LED fog lights. I'll make sure the wires are all taped up and don't tap anything. I was also thinking of putting Dynamat to dampen road and wind noise as well...

 

I have some dynamat in the front doors. I thought it might improve the sound performance from the new speakers I installed. Didn't make much difference to me.

If anything some additional sound proofing of the firewall or under the hood might help with the engine noise.