Are you using cutter comp? This forces the control to look 5 steps ahead. It may help. I owned a BOSS 9 back in 1996 but cannot remember how I overcame the hesitation. It was not that bad for me. There is a G code that changes the feedrate automatically as the cutter goes around the inside or outside of a radius. It is used to keep a constant chipload on the cutter. You could try playing with that also.
If you are doing 3D milling with a program generated by a CAM system, then your steps are very small, the programs are long and the processing speed of a control designed in the early 80's may leave a lot to be desired.