What was found
(CAN) AIRCRAFT REPORTED STALL/SURGE AROUND 60-70% DURING ACCELERATION AND DECELERATION. PILOTS REPORTED THE DEFECT ON THE#1 ENGINE, HOWEVER UPON INVESTIGATION THE ENGINEERS REPORTED IT ON BOTH ENGINES. CUSTOMER CHECKED THE BLEED SYSTEM AND CONDUCTED A CAPPED RUN ON BOTH ENGINES , SURGE WAS STILL PRESENT. THE PAC RESULTS SHOWED NH AND NL MARGIN ALMOST ZERO. BOTH ENGINES HAVE TO BE SENT TO SHOP FOR PERFORMANCE RESTORATION. (P&WC) (TC# 20190628009)