What was found
AFTER ENGINE RUN START LEFT LEFT DUCT PRESSURE INDICATOR SHOWED 9 PSI AND THEN A SPLIT BETWEEN LEFT AND RIGHT INDICSATORS OF GREATER THAN 20 PSI ABOVE IDLE. GROUNDED - YES. PERFORMED ENGINE AIR BLEED HEALTH CHECK AND FOUND HIGH STAGE REGULATOR AND HGH STAGE VALVE AT FAULT.REMOVED AND REPLACED HIGH STAGE REGULATOR REF MM 36-11-07-000-801 AND 36-11-07-400-801 AND REMOVED AND REPLACED HIGH STAGE VALVE REF MM 36-11-06-000-801 AND 36-11-06-400-801 OPS AND LEAK CHECK GOOD.DUCT PRASSURE HOLDS STEADY FOR BOTH SIDED @ 20 PSI.GROUND VERIFICATION SUCCESSFUL.