What was found
AT CRUISE FL 400, THE RT ENGINE BECAME ERRATIC WITH EPR FLUCTUATIONS BETWEEN 1.10 TO 1.29 WITH ASSOCIATED VARIATIONS IN N1 AND FUEL FLOW. TURNED AUTO THROTTLES OFF AND THE PROBLEM CONTINUED. REDUCING POWER DID NOT HELP. R & R RT(NR 2) ENGINE EEC IAW AMM 73-21-04-4-0. PERFORMED EEC STATIC TEST IAW AMM 71-00-00-5. TEST PASSED, NO CODES DISPLAYED ON EPCS PAGE. RAN BOTH ENGINES IAW JRH. ALL INDICATIONS STABLE AND NORMAL. RECHECKED FOR CODES ON EPCS AFTER ENGINE RUNS. NO CODES PRESENT. ACFT OK FOR SERVICE. INSTALL BORROWED PART AND REMOVE OPERATOR PART.