After overhauled engine starting TIT 700 deg.Null start 760 deg then changed TD valve,Td calibaration ,All thermocouple checked and replaced new with T-block and harness,throttle rigging ck,blade angle ck,but problem still.all other throttle setting fuel flow, TIT,torque,RPM, are fine.perform rich lean check TIT drop 35 deg instant of 100 deg.Is it downstream burning or FCU faulty. takeoff TIT =977 FF= 2100,Torque=16500 inch lbs cross over =760