Not very xtraordinary (since that is a racecar) and it has the T6 enginge from S80, a friend of mine have 350++ hp in his s40 now (4 cylinder, 2.0T). Streetlegal.
Now he has ordered a new engine from Autotechmotor www.atechmotor.com (swedish page only ) and it will be over 400++ hp when it's ready.