As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LAS - YVR - EL - FLT 437 - LOG 7628896. CREW REPORTED DURING CLIMB BOTH ENGINES WERE SURGING. CREW DECLARED AN EMERGENCY AND RETURNED TO LAS. MX REPLACED NR 1 ENGINE PRESSURE REGULATOR VALVE IAW AMM 36-11. MX ALSO REPLACED THE ZONE CONTROL VALVE. OPERATIONAL CHECK WAS GOOD. A/C PASSED CHECK FLIGHT. A/C WAS RETURNED TO SERVICE.