Another thought-
I have had cars with vibration that turned out to be bad injector connector, bad temp sensor, failing coil-on-plug. One way to confirm mechanical vs other source is to coast down from speed, in gear (engine braking). That minimizes any contribution from fuel or spark- if you don't feel vibration then, it's likely not caused by the major rotating bits.
Whoever said it should be smooth is right, my old 3.0 feels like a turbine when revving, accelerating, or engine braking. Lumpy at idle of course.
Dan
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