What was found
AT FL 390, ACFT SHUDDERED WITH A ASSOCIATED POP. EGT WENT INTO RED, FOR RT ENGINE. IMMEDIATELY BROUGHT RT THROTTLE TO IDLE. EGT WAS IN THE RED APPROX 15 SECONDS AFTER THROTTLE WAS AT IDLE, MOTOR RAN NORMALLY AT IDLE. CAPTAIN STATED THAT HE OBSERVED THE RT ENGINE EGT IN EXCESS OF 935 & THAT IT WAS APPROX AT THAT TEMPERTURE FOR 10 TO 15 SECONDS. REMOVED RIGHT ENGINE PER W/C 71T0002-RR AND INSTALLED SERVICEABLE ENGINE PER W/C 71T0902-RR. ALL REQ'D ENGINE RUNS COMPLETE. ACFT OK FOR SERVICE.