Engine Vibration at 2000rpm
 

I have a 1993 N/A Toyota supra, the clutch began slipping so I bought a replacement...
To void warranty I had the flywheel machined... After putting everything back together there was a strange vibration at 2000rpm which is quite evident.
I placed put the car back on the hoist thinking that I might have placed the flywheel incorrectly and it wasn't counter balanced correctly. However, I placed the flywheel on the 8 ways in which it would go and it was the same in every turn. Vibration.
I then mounted the clutch to the flywheel, the same result.
So I put everything back together, bellhousing etc.
The result was different, the vibration was now in the range of 2200 to 2500rpm in neutral and in gear...?
I did look at the engine mounts, and they seemed to be okay...

I am not sure whether I should be worried about this... I am worried it is wearing on the engine, bearings etc. It just doesn't make sense...
Any help would be appreciated.

Also, off topic but does anyone know much information on why the two front seats in the Supra are not the same material as the rear (leather)..

Thankyou.