What was found
AT CRUISE FL 350 (4+ HOUR CRUISE) L DUCT PRES 18 PSI / R DUCT PRES 40 PSI (L DUCT PRES APPEARS TO VARY BETWEEN 18 PSI AND 20 PSI). AT TOP OF DESCENT FIRST THROTTLE REDUCTION R DUCT PRES FLUXUATED AND REDUCED TO 19 PSI / AT THE SAME TIME L DUCT PRES STAYED SOLID AT 19 PSI / DURING DESENT L&R PRES STABILIZED AT 19 PSI / AT 10 000 FEET L&R PRES WAS STABILIZED AT L 30 PSI / R 30 PSI. COMPLETED NR 1 & 2 ENG HEALTH CHECK NO FAULTS ON NR 2 ENG FOUND NR 1 ENG HIGH STAGE VALVE WON'T SPRING CLOSED REPLACED NR1 HSV REF. MM 36 11 06 REPLACED NR 1 ENG PRSOV REF MM 36 11 04 NR 1 ENG BAR 390 DEG SENSOR & 450 DEG THERMOSTAT. ACCOMP ENG BLD AIR CROSSOVER TEST REF MM 36 11 00 710 801 OPS CHECK GOOD.