If it's your guibo you can see it right away no need to turn anything, when you are under the car jack up your engine slightly from left and right side (use board/common sense) and see if mounts allow out of spec movements, do the same for transmission mounts. In these cars the culpit for vibration is usually motor mounts. Also check your fan clutch for seizing. The diff bushing will be PITA to fix but you can visually inspect it as far as I can recall.
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