Chan HT

Hi, my car, WRX MY 98, RPM needle will jump from approximately 4000 rpm to 6000 rpm and from there, rpm needle flickers between 6000-7000 rpm at full throttle but engine/car accelerate smoothly. With light throttle, rpm needle will move up smoothly all the way to 6000rpm with no rpm needle flickering at all.
Is the rpm gauge dying ? RPM needle will not flicker at all if engine without load. ECU is Link ECU with 400 cc injectors.
Any advice ?
Thanks.

Chan