Originally Posted by
casino57
Not really. Narrowing the rear of the car will give your car some push. It actually make more rear traction.
But based on what Hagberg has said about the mod to me it suggests more steering which would be less rear grip:
"This mod makes the rear of the car quite a lot narrower which results in more turn-in and mid corner rotation. The car will be more aggressive and difficult to drive but faster for some conditions."