Thats not compressor surge.
On our cars it sounds like a bird chirping and goes away at around 3800rpm when valve lift occurs.
On all our maps on JB4 the torque ramp up is low to avoid this.
George, is the noise being generated by the DV bleeding boost off? The "bird chirping" is the best explanation I've heard for it
Now with my DP and CTS Turbo Inlet tube (JB4 /w map2) the bird chirp is much more audible and happens sometimes at low cruising speed with steady throttle.