The performance pack has been developed alongside Volvo and having it fitted won't have an impact on a car's factory warranty.
The first S90/V90 models to be offered with the Polestar upgrades are those equipped with the D5 PowerPulse diesel engine. With the pack fitted, the 2.0-litre engine's output grows from 232bhp and 354lb ft of torque to 237bhp and 369lb ft of torque, and the car's throttle response settings have been sharpened, along with gearshift speeds.
Volvo says the finished product is more dynamic and therefore more fun to drive.
Polestar boss Niels Möller said: "We have received strong feedback over a long period of time from customers all over the world regarding Polestar performance parts. We are delighted to now be able to meet that demand.”
The performance equipment has been developed by Polestar, which has 20 years of motorsport experience, as well as its motorsport partner Cyan Racing. It is Volvo's official tuning partner.
Polestar’s research and development director, Henrik Fries, said: "Lessons learned on the track are transferred directly into the development of our road cars and performance products. The new range of Polestar performance parts is no exception; they are designed and developed with the very same philosophy.”