Originally Posted by VinceThe1

The reason more than likely is because of your tire sizes. First, your rear tire is a whopping 8% (6.6") larger in circumference than original, but that's not the problem.

The problem is that you have a 4% (3.5") difference in circumference from front and rear tires, this would throw the VDC ecu off because your front and rear axles will be turning at different speeds without any steering angle.

Your front tires will be spinning faster than your rear on the axle, making the VDC ecu think there is wheelslip (although impossible due to the fact the Z is rwd and there's no way the fronts would be spinning faster than rears unless you're locking up the rears with the e-brake but that's beside the point, it still throws off the computer)

Three different ways to solve this:

1. Turn off your VDC everytime you start your car.
2. Replace rear tires with 325/30R20
3. Replace all tires with tires that are closer to factory diameters like 275/30R20 front and 325/25R20 in the back.

Originally Posted by F.I. Inc.

Yes, they are Tony approved! Frank, when I get around to it, I may put your pipes into production. We will call them, "The FP" option.
-Tony