Jimmy,
I have had a similar problem since I had my 1.8t revo'd. Mine is great on light throttle but if on full throttle around peak boost (3000 rpm ish) I get this surging / hesitating that you mention from then on throughout the rev range. I have replaced many things to get to the bottom of this including n75, uprated divertor valve, many solenoids, temp stats (intake and coolant), coil packs, spark plugs, 3X Maf's, fuel filter and Vac pipes but it still does it.
After many Vagcom runs monitoring knock, intake temps, boost levels etc we have concluded that it's detecting pinking (Knock) and this surging is the timing being cut back by the ecu then being brought back in again. One theory we have at the moment is that under full throttle it's not getting enough fuel so leaning out on peak boost, pinking then getting into this hesitation / holding back cycle!
I have even monitored real time fuel pressures and it always meets required book pressure but a fuel pump can give correct pressure but not give correct flow. As yet I have not replaced the fuel pump relay (next on the list) or fuel pump itself to see if that is the cure.
To note a good super unleaded fuel will lesson this effect due to its high octaine, I have turned down my revo settings to those below the standard Boost 6 timing 2 and still get this problem.
I have spoken to various people about this problem and it has been suggested that the duel mass flywheels can start to break up and cause knock but this is normally only detected on cylinders 3 & 4 mainly high on 4. I get the same levels of knock across all 4 cylinders so that rules that one out for me!
Pm me if you want any more info, this might not be exactly the same thing that is happening to your car but it might help point you in a certain direction.
If you do solve this problem before me let me know !