[GTLEGEND]

Check the engine mount under the coolant reservoir. Its basically a aluminium frame with a mount inbetween. The best way to check is if the bottom of the rubber has made contact with the top of the bottom aluminium piece, then the mount is gone. You will see rub marks if it has collapsed. In normal operation the rubber will not touch the aluminium surround. Once you look in person, you will see what I mean. The rubber collapses and touches the lower aluminium.

Also check for tune issues usually spark plugs or coils which with age can have small cracks which causes a slight miss fire and then a vibration is felt.

Has this had the transmission removed or a clutch replacement in its time? Sometimes if the clutch mounts are not torqued to spec and in the specific sequence, a vibration can also be felt.

These are the most common causes of vibration in these things.