As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT DUCT PRESSURE SURGES BETWEEN 20 TO 50 PSI DURING CHANGES IN ENGINE POWER SETTINGS. DISCOVERED LT ENGINE PRSOV INLINE FILTER FREE OF DEBRIS, PLUG HAD TORN PACKING. REMOVED AND REPLACED PACKING. PRSOV OPS CHECK AND DUCT PRESSURE MODULATION CORRECTED ON ENGINE RUN IAW FIM 36-10-01.