As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE FLIGHT, PLACED RIGHT FUEL SELECTOR TO LEFT MAIN FUEL TANK, BOTH RIGHT AND LEFT ENGINES SHOWED SIGNS OF FUEL STARVATION (ENGINES SURGING). PUT LEFT FUEL BOOST PUMP ON LOW AND WAS OK. FOUND LEFT AUXILIARY BOOST PUMP INLET CHECK BALL STUCK ON SEAT RESTRICING FUEL FLOW WHEN BOTH ENGINES RUNNING OFF LEFT TANK AT HIGH POWER SETTINGS.