I found this on another forum this might be it.
Some of the LS7 engines are becoming plagued with a dry sump oiling system noise that mimics a rattle sound, coming from the right dash board area, and it's enough to drive you cuckoo.
GM actually tried to say it was normal, a byproduct of the LS7 engine (ear plugs included) LOL
GM says attempt NO fix at this time as it would be an admission that there is a problem and don't suggest a fix to the customer, they don't want it known there is a real problem, and they have NO FIX for it yet.
Also see this thread
Rattle FIXED!!!
Also Post 14# from this thread
Brand New Z06 - Help!! - Corvette Forum
