This is how I understand it and may help you out so you know what you are experiencing and what it anything can or needs to be done about it:
There is a difference between surge and stall. What you are likely referring to is stall. That is the sound of air rushing back out past the comp wheel when you quickly let off the throttle while you are under boost. Also you will hear it when the trans shifts.
Surge happens when you are actually on the throttle under boost and you will hear whop whop whop sound this will also be accompanied by the actual boost fluttering up and down much to the tempo of the sound. What is happening is the comp wheel is actually getting getting ahead of the air its is forcing into the engine. This allows it to spin up but then its hit by the pressure equalizing and it suddenly has that force applied to it again. This is where you see the boost drop thru spike up a bit. The issue is its putting stress on the bearing as its thrust one direction then the other.
So the two big differences are one is when you let off the throttle the other is when you are on it. The other is that surge the latter of the two described above is the most damaging. Stall is something all turbos will have unless they have an anti stall setup which has a port, hose that routes air back around the comp to equalize pressure when load is suddenly dropped.
The reason many get surge after they have tuning changed ( have the truck chipped) is the fueling is changed. Usually to heavy fueling at some point in the curve is what I have heard. Different tuners different tunes will all act somewhat different with different levels of surge. I never noticed it with Matts tunes but had it with TW of the two TW IMO was fueled heavier down low.
What changing the stock SD wheel to the smaller Van wheel does is changes the map. It changes specifically the ratio of boost to shaft or wheel speed. This prevents the wheel from starting to surge as tech it is not able to move as much air per rev.
