I have a 2007 sts with a northstar engine that has developed a bearing noise. When I brought it to the dealer under warantee the said it was normal and as long as the engine was running they wouldn't do any thing. The car sounds like a deisel going down the street. The dealer said it was a design flaw and replacing the parts might give the same results. Gm said they can't do any thing unless the dealer says so. When you pay almost $50,000 for a car you would expect some support. Maybe that is why they stoped making this engine? Like I said if the problem is in the engine forget the warantee.