What was found
AUTO PILOT DISCONNECTED AFTER LEVELING FL340. ALTIMETERS LEFT AND RIGHT INDICATED 400' HIGH. MULTIPLE EICAS : "AIRSPEED UNRELIABLE" " ENG EEC MODE R" "ENG EEC MODE L" " GND PROX WARN". ATC READOUT SHOWED 300' LOW WHEN WE RETURNED TO FL 340'. EICAS BUTTON DEPRESSED. DECLARED EMERGENCY. AMM: 34-21-03-4, AMM: 71-00-00-5, ALL EICAS MSG RELATED PITOT ADM PROBLEM. REPLACED RT PITOT ADM AND CYCLED AIRCRAFT POWER THEN ALL STATUS MSG DISAPPERED. CONFIRMED BOTH ENG RUN CHECKED NORMAL. A/C OK FOR SERVICE.