Had virtually the same problem with mine. Started a slight vibration at 2000 and went away at 2200. Turned out that the pushrod between the clutch slave cylinder and the arm for the throwout bearing was too long (found the problem after the clutch slipped a little under hard acceleration). Apparently the clutch had worn some after 1500 miles and I hadn't left enough slop in the pushrod (had the slave cylinder piston all the way to the bottom). Removed the pushrod and shortened it about 3/8 of an inch and now everything is much better. Still vibrates a little bit if you're looking for it but otherwise not noticeable. I suppose that clutch linings can and will wear unevenly if you let them get out of adjustment. Just a thought
h dog