As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: ENGINE #2 VIBRATION HIGH ON DEPARTURE. WITNESSED AS HIGH AS 9.9.PULLED #2 ENGINE BACK AND IT LOWERED WITHIN PARAMETERS. WHEN THRUST LEVEL PUT BACK IN, ENGINE VIBRATION REINTRODUCED. WENT REMAINDER OF FLIGHT WITH THRUST REDUCED AND REMAINED WITHIN PARAMETERS. RTB AS A PRECAUTION. DECESION MADE TO RETURN TO MIA. EMERGENCY DECLARED, AIRCRAFT WAS OVERWEIGHT FOR LANDING AND MET BY ARFF AND TAXIED TO GATE. MAINTENANCE REPLACE ENGINE VIBRATION MONITIORING UNIT IAW AMM 77-32-34.