So after too many months of diagnosing and tracking down noises, I have discovered that the Center Diff Bearings in my Outback XT 5MT are shot. I ran it up on jack stands the other day and the sound it makes is just cringe worthy. After much research it seems as though this happens more often than it should. Never the less, I am going to do the repair myself, the hardest part is finding a shop that can press the bearings but I have a few leads. I am really looking forward to not putting up with that constant howling noise on long trips!