The balance of the pulley itself is not really the issue. Its the mass of the pulley itself. With a lightweight pulley and flywheel you change the location of the CG of the crankshaft, and its vibration characteristics will change. The 1.8t has proven to be very sensitive to this change.
I will second Brett’s recommendation of the Fluidamper or the stock pulley. The performance increase of a lightweight flywheel is much much more than the crank pulley anyway.
Nice build! :thumbup