My old clutch in MY S13 made a vibration around 2000-3000 rpm, funny thing was it did it, but then we removed the clutch and put it back in and the vibration went. I'm guessing it was a balncing problem or we never put the plates and sandwich plates in the right way (ie alternate holes line up hole or not??) Hard to explain but yeah look at the way the plates go in and you'll understand.