YOU HAVE YOUR TERMINOLIGIES MIXED UP.SURGE IN GAS TURBINES NORMALY HAPPENS AT FAIRLY LOW N1 SPEEDS<80% IT IS CAUSED BY THE AIRFLOW THROUGH THE ENGINE STAGNATING .IT IS NORMALY PREVENTED BYTHE ENGINE BLEED VALVE WHICH WILL CLOSE AT A PRESET N1 DEPENDING ON AMBIANT AIR PRESSURE AND TEMPERATURE.HUNTING IS SOMETHING ELSE,GAS TURBINES IN PAIRS DUE TO THE GOVERNING SYSTEM MECHANICS WILL POWER SHARE WITHOUT ANY EXTERNAL CONTROL,HOWEVER IF ONE ENGINE N1 SPEED STARTS TO HUNTTHE OTHER ENGINE WILL COMPENSATE FOR THE INCREASE OR DECREASE OF TORQUE AS ITS GOVERNING SYSTEM WILL DETECT THE FLUCTUATION IN ROTOR RPM.IN MY EXPERIENCE ENGINE GOVERNING SYSTEMS THAT USE AIR IE BENDIX ECT ARE PRONE TO THIS NORMALY DUE TO AIR LEAKS.