As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WITH POWER INCREASE UNUSUALLY HIGH AIRFLOW IN THE FLT DECK LEFT PACK GOES TO ABOUT 50 PSI AT 40% N1 WITH RIGHT STAYING ABOUT 32 PSI. GROUNDED - YES. REPLACED L/H PACK FLOW CONTROL VALVE REF B737-800 AMM 21-51-02 NO LEAKS NOTED, AT 40% N1 L PACK AT 31 PSI, R PACK 26 PSI.