Pretty neutral, as I have a 20mm rear anti-rollbar (sway-bar) fitted* from a Touring (Bought new from BMW £70 $140).
I am not a good enough driver, nor have I anywhere near enough racing experience to say whether this is actually superior to the OEM setup when on a track at 10/10ths driving, therefore I've traditionally kept quiet about it.
I do find that the traction available when accelerating hard off roundabouts or down slip-roads (on-ramps) is superior to what it was before, but when the back does snap out it requires a faster response to catch it.
Therefore I may have a faster point-to-point road-car yet a slower track-car compared to standard, I could not say.
Kind Regards
Ivan
*My thinking thinking goes along the lines of;
BMW fitted 18mm to the 3.6 car when new, setting the car up as minor factory understeer for road safety with standard 235/40/17 at all four corners. This badly understeers with the optional wider 9.0J" rims which had 255/40/17.
In 1992/3 they then fitted the wider rear 17" wheels as standard, but changed the rollbar to 19mm to compensate, still leaving the car as quite biased towards understeer, as per normal with any normally sold road car.
As I have increased the rear tyres even more over factory default, I have added the 20mm bar to compensate. As the rigidity of the bar goes up non-linearly with diameter increase, (the 19mm to 20mm resistance to torque is more than the 18mm-19mm value), this dials out the understeer leaving a neutrally balanced car. That's Plan A, anyway!
Plan B? See Plan A.
The experiment is ongoing, as tyres perform different when new as when old, plus I've been through several different makes and compounds, all which takes time. I am well aware of Mr Farrell's oft quoted and correct maxim that Grip and Traction are not the same thing.
I continue to experiment as I know BMW had tyre price, longevity and NVH to consider with their factory choice, none of which bother me any. As 18 years have passed in tyre design and performance since my car rolled off the production line, I consider I have carte blanche to goof about!
.