As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NR 2 ENGINE HAD A LOW FREQUENCY VIBRATION AT POWER SETTING ABOVE 65 PERCENT N2. FLIGHT RETURNED TO DTW AND LANDED WITHOUT INCIDENT. THE ENGINE WAS INSPECTED AND BORESCOPED, NO DISCREPANCIES NOTED. MAINTENANCE REPLACED THE FUEL CONTROL UNIT RESTRICTOR TUBE WITH A SERVICEABLE UNIT. THE ENGINE WAS RUN UP AND CHECKED OK. AIRCRAFT RETURNED TO SERVICE. CORRECTED COPY: CHANGED A/C TT AND A/C TC.