What was found
RT ENGINE VIBRATION WITH ASSOCTAED RISE IN ITT - APPROX 2 HRS INTO FLIGHT AT FL430 THE NR 2 ENGINE, N2 VIBRATION MOVED FROM 5 PERCENT TO 30 PERCENT SCALE THE ITT WENT FROM 809 TO 826 N2 WENT FROM 99.0 TO 100.4. AFTER A FEW MINUTES EVERYTHING RETURNED TO NORMAL EXCEPT THE N2 VIBRATION. 1 HOUR LATER WHILE DESCENDING THROUGH 14000 FT THE N1 VIBRATION WENT FROM 5 PERCENT SCALE TO 30 PERCENT SCALE. THE "FUEL 2" ANNUNCIATOR CYCLED 4 TIMES OVER A 5 MINUTE PERIOD THEN THE N1 VIBRATION RETURNED TO NORMAL, BUT THE N2 VIBRATION REMAINED AT 30 PERCENT. SUPP: REMOVED NR 2 POS ENGINE SN P105418 AND INSTALLED REPAIRED RENTAL ENGINE SN 105458, PERFORMED WORK. IAW AMM TASK 71-00-01-900. COMPLIED WITH ENG RUN UP INSPECTION IAW AMM 71-00-00-910-802.