You might want to also post this in the warranty/complaint thread. It could be something as simple as a heat shied rattling.
You should also check to make sure everything it tight (spoiler bolts, etc).
If the noise sounds like it coming from behind/under the glove box area, it could be the coolant restrictor. It makes weird noises under load coming from behind the glove box that sounds like it be coming from the transmission. I had to have some parts replaced on my car to stop a weird noise from that area. TSB 09-01-37-001