Your "more power, no more traction" sentence conveys the idea that the car's tires can't handle the torque. With the old 510 horses the rear tires were actually quite reluctant to spin in first gear, at least while going straight. If the power was rolled on smoothly that tires would grip with little drama. If the car was much lighter that wouldn't be true anymore though, because there would be less weight to hold the tires in place.