Is the noise a ghostly moan that only occurs in temperatures below 40F, that goes away a few minutes after start, and changes pitch with engine RPM? If so, this is rather common on 850's. I've read numerous posts on this board asking about it, but I've never read an explanation. It started on my '94 when the car had 14000 miles (in 1995) and continued to the day I sold it a couple of months ago. The dealer could never find anything wrong, so I learned to live with it. In my case, it was definitely not the air pump, oil pump, timing belt (including tensioner, etc.), or anything turned by the accessory drive belt.