As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LT DUCT PRESS FLUCTUATES BY 20 TO 30 PSI DURING DESCENT. THROTTLES IDLE. REPLACED HI-STG VLV STILL FLUCTUATES 10-14 PSI. NEED FURTHER TROUBLESHOOTING. NEEDS NEW SUPPLY PRESS HOSE ASSY, B-NUT THREADS DAMAGED. REPLACED LINE, NO HELP. REPLACED HIGH STAGE VALVE, NO HELP. NEEDS FURTHER T.S. VALVE LOCK IAW MEL REPLACED NR1 ENGINE PRSOV VALVE (SN 1176) AND THE HIGH STAGE PILOT VALVE (PN 3399004, SN 162).