As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DUCT SPLIT OF 23 PSI OBSERVED AT FL390 AT M785. RIGHT DUCT SHOWS 21 PSI AND LT SHOWS 44 PSI. THE DUCT SPLIT VARIES FROM 23 PSI-18 PSI AT DIFFERENT POWER SETTINGS WITH THE RT ALWAYS INDICATING LESS THEN THE LT DUCT. ACFT GROUNDED. PERFORMED TC NG-36WC-00001 BLEED HEALTH SYS TEST ON NR 2 ENGINE. FOUND HIGH STAGE REG VALVE FAILED REVERSE FLOW DIAPHGRAM CK, REPLACED HIGH STAGE REG VALVE, REF 36-1107. PERFORMED OPS TEST IAW FIM TASK 36-10-807.