As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB FROM FLT 380 TO FL400 LEFT AC DUCT PRESSURE WAS 45PSI, RT PRESSURE WAS 19 PSI. (A 26 PSI DIFFERENCE ON LEVEL OFF FL 400 WITH POWERBACK AT CRUISE (90.4/90.2 N1 RESPECTIVELY) LT PSI WAS 37 PSI AND RT SIDE WAS 21 PSI. R & R HIGH STAGE REGULATOR, PRECOOLER VALVE AND HIGH STAGE VALVE ON NR 2 ENGINE REF MM 36-11-03-000-801, 36-12-02-000-801 AND 36-11-06-400-801. ACCOMPLISHED T/C NG-36WC-00001. LK CK GOOD.