As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
POWER FLUCTUATION DURING TAKEOFF. DURING CLIMB AT F 50 ACFT SUDDENLY YAWED ENGINE NR 1 EPR DROPPED TO ZERO ALONG WITH N1 THEN RECOVERED IT APPEARS THE ENGINE LOST POWER THIS OCCURRED THREE TO FOUR TIMES THROUGH FL 70 WHERE DESCISION TO TURN BACK WAS MADE, DURING DECENT AWD ON APPROACH ALL ENGINE PARAMETERS WERE NORMAL. R & R NR 1 ENGINE MAIN FUEL FILTER, R & R NR 1 ENG FMU, R & R NR 1 L/P HP FUEL PUMP. ACCOMPLISHED HIGH POWER ASSURANCE TEST/ENG RUN. NO FAULT NOTED. ALL CHECKED OUT OK. ACFT RETURNED TO SERVICE.