As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DUCT PRESSURE DURING T/O AND CLIMB, UNTIL LEVEL @ 32,000 RT 43 LEFT 20 PSI. AT CRUISE LEFT 30 RT 39. GROUNDED - YES. COMPLETED TASK CARD# NG-36WC-00001: NR 1 ENGINE BLEED AIR HEALTH CHECK STEPS 1-5. REMOVED AND REPLACED PRE-COOLER CONTROL VALVE REF AMM 36-12-02-000-801 AND AMM 36-12-02-400-801. BLEED CROSS OVER OPTS TEST REQUIRED. BLEED AIR HEALTH CHECK GOOD REF AMM 36-11-00-710-801. NO FURTHER DEFECTS NOTED.