What was found
ABNORMAL DUCT PRESSURE SPLIT DURING CLIMB, DELTA PSIG LESS THAN/EQUAL TO 20PSI, FL 280, LT PAC 30, PSI-R PAC 48, PSI. N1 98.9 CLIMB. FL 300, LT PAC 30, PSI-RT PAC 39 PSI-WENT TO 50 PSI THEN TO 48 PSI IN 10 SECONDS N1 99.7. FL 330, LT PAC 29 PSI-RT PAC 49, PSI N1 100.7 CLIMB, FL 350 LT PAC 31 PSI-RT PAC 46 PSI, N1 91.8 CON GREATEST PRESS SPLIT OBSERVED 20 PSI. ACFT GROUNDED. IAW TECH SERVICES REQUEST, ACCOMPLISHED T/C NG-36WC-00001, NR 1 ENGINE BLEED AIR SYS HEALTH CHECK. R & R HIGH STAGE REGULATOR IAW AMM 36-11-07-400-801. LEAK CHECKED GOOD. R & R PRECOOLER CONTROL VALVE IAW AMM 36-12-02-400-801.