As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DISCREPANCY: DUCT PRESSURE DIFFERENCE IS BECOMING LARGER. LEFT SIDE IS 15 PSI LARGER THAN RIGHT SIDE. CORRECTIVE ACTION: REPLACED PRESSURE REGULATING VALVE CONTROLLER AND OPS CHECK GOOD AMM 36-11-19, GROUND CHECK GOOD. AC REMAINS ETOPS.