Took the car to the local Subaru dealership today (Subaru of Gwinnett). They found the noise problem....
One of the clips for the airbox was broken - causing the air box to not sit properly - and probably move a round a bit under acceleration. They put a new clip and the noise is gone. It is amazing how loud the intake is - I would have sworn it was an exhaust problem. Its also amazing how I could have been so dense as to have missed that.
Thanks Subaru of Gwinnett!!