When tuning, under "Others" and then "For Professionals" there should be the VCD controller or variable center differential. This will allow you to adjust the torque balance.
No you can't do this in GT2. PD didn't start offering VCD until GT3. The Yaw control (AYC) you've got there is for a few Mitsubishis only, but it's not the same as VCD.
Your best bet is to mess around with a full-custom limited-slip device, which helps control front to rear torque delivery much better than the yaw controller.
