What about your motor mounts? Just a thought. You have checked and done everything I would think of, I would however install new motor mounts, and loosen the trans rear mount, and the exhaust hangers that connect to the tranny, start the engine and let it warm to operating temp so that the engine settles and the exhaust expands. Then go in and retighten everything up to ensure it is positioned well. Is the vibration coming from the rear? What about your half shafts? Have you checked those, sometimes when it is a noise or vibration during acceleration one would think the rear end, if it quits when you let off the gas? Does it seem like a balance vibration or a mechanical vibration? Remember these cars are really tight, vibrations and noises travel really well, I had a humming in my S 140 once, could not find it, finally had to take it to an expert at the dealership, it was the drivers rear bearing, It sounded like it was everywhere in the car. Good luck!
Brian

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Brian W. Heitman

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