I have a 2004 coupe bought new. Replaced the rear diff at 10000 miles, and the second one at 30000 miles. Tech said he did not hear any noise. Took the service manager for a ride, and showed him. Same kind of story as your guys, noise when you are higher than forty mph. Goes away when you lift the pedal. Bearings are loading up under load. Good to hear you guys got results as well.