I have had this issue since I purchesed this car back in 05 and put it away for 5-Years.
Everything is new, Plugs, wires, cap, rotor, valves adjusted, vacuum lines and leaks accounted for.
It idles rock steady at 650 or so, this is a vibration issue not an unsteady idle. New motor mounts this week I am going to place a jack under the tranny and see if this changes anything. I also understand that an alternator mounting bushing may go bad and am starting wondering about my cats being plugged.