Here is the answer i got from Teslas productsecialist:
All about Perf + :
The Performance Plus suspension tune was developed with the driver in mind. The re-tuned dampers add a very comfortable, yet firm ride that help to transform the Model S into a driver’s car. The dampers work with an updated rear suspension, which boasts an array of new bushings that increase the lateral stiffness and help to spice up the back of the car without compromising comfort. The steering response comes as a direct effect of the dampers and bushings, reducing the delay between the driver input and the vehicle response. This brings you more in tune to your Tesla, and the road beneath it. To tie your Model S Performance Plus to the road, the 21” wheels are wrapped in larger Michelin Pilot Sport PS2 tires on the rear, which helps the driver unleash what the Model S Performance Plus is truly capable of; precision handling that allows the driver to maintain a desired trajectory without any correction.
Below is a list of upgraded components and how they help to create the Model S Performance Plus:
Stabilizer Bars – In a typical “performance car”, large stabilizer bars can corrupt the steering and degrade the ride; but not in Model S Performance Plus. Thanks to our low center of gravity, we have increased the stabilizer bar size front and rear without the negative side effects, allowing greater body control and more predictable handling.
Damping – Tesla’s philosophy on damping is to maintain good handling behavior with good control, while also adhering to a supple ride. The damping characteristics available on the Performance Plus help to bring feedback from the road to the driver to enhance your driving experience, but still manages to encompass road undulations with ease.
Bushings – Tesla focused their attention on increasing lateral stiffness at the rear suspension to improve steering and overall vehicle response. This has been achieved by new and improved compliance characteristics throughout the suspension, thus allowing the springs and dampers to work more efficiently.
Tires – Performance Plus sports new Michelin Pilot Sport PS2 tires on a wider rear wheel, which allows its higher performance threshold to take advantage of the improved lateral stiffness of the car.