Mine does this too. I chalked it up to my BOV being too tight. I loosened it up and seems to be better.

Mine would happen on part throttle boost in higher gears. if I nailed on it WOT in those gears it would be non existant (at least to my ears and feeling wise)

Mine was bad enuff though that I think it would affect safety if doing mild boost in a little curvy area. It would jerk all around when surging.

For the record, my car has a Forged Motorsports Type Rs bov recirc. The dude I bought it from had it at FULL Tight though for some reason.

 

In you increase displacement, everything else being equal you will decrease the area on the efficiency chart where you have surge for a certain RPM/Pressure combination.