What was found
AT FL380, THE RIGHT PACK OFF LIGHT ILLUMINATED ACCOMPANIED BY EICAS MESSAGE. UNCOMMANDED REDUCTION IN AIRSPEED AND NR 2 ENGINE POWER OCCURRED. MANUAL THROTTLE MOVEMENT INEFFECTIVE. EMERGENCY DECLARED. FLIGHT DESCENDED TO FL280. ENGINES AND PACKS RETURNED TO NORMAL. EMERGENCY CANCELLED. AIRCRAFT GROUNDED. TROUBLESHOT NR 2 ENGINE TPU, BVCU AND EEC, BOTH PACK CONTROLLERS, THE MCDP AND PLA ALL WITH NO FAULTS FOUNDED. ACCOMPLISHED RUN OF BOTH ENGINES IAW AMM 71-00-00 WITH NO ANOMALIES NOTED. FDR SHOWED NO INDICATION OF NR 2 ENGINE ROLL BACK.