As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: WHEN POWER WAS ADDED FOR TAKEOFF LEFT ENGINE BLEED AIR DUCT PRESSURE SPLIT +20 PSI FROM RIGHT ENGINE AND UNSTABLE CYCLING +-20 PSI. REPLACED NR 2 ENGINE PRESSURE REGULATING SHUTOFF VALVE (PRSOV) AND ACCOMPLISHED A SATISFACTORY LEAK AND OPERATIONAL CHECK PER AMM 36-11-09.