It does both. If you fit a thicker ARB it reduces the maximum amount of grip at that end of the vechicle. So to reduce understeer you need to reduce rear end grip or push that the rear generates. Go too far and the car will be tail happy and potentially dangerous for people not expecting it. If you look at this video it's me in my car at Curbrough sprint course quite a few years ago now. You can see that occasionally the car is tail happy when provoked, and on acceleration you can get the rear breaking free a bit. This helps rotation and is a more interesting way to drive. The B8 quattro is a 60/40 torque split rear to front. The chirping noise from the exhaust was because of a mod I made to the DPF. Doesn't do that now.