Torque steer shouldn't have much to do at all with how much power is going to each wheel. With properly designed suspension and properly off-set wheels one tire could bear all of the load without causing the wheel to jerk.
Generally torque steer is caused by an irregular change in the suspension geometry under load. On the Viggen the bushings flex, the subframe flexes, and the steering clamp is not mounted rigidly enough to stop even the normal steering load from allowing it to move. All these things together cause the geometry of the suspension to change significantly.
When the subrame is under accelleration load on the Viggen the rear control arm mounts move outward slightly. This does not cause torque steer as long as both wheels grip evenly. However when one wheel loses grip, the other suspension mount flexes more because it's pulling forward with more force. This causes that wheel to point slightly inward, which pulls on the steering tie rod ends and jerks the wheels in the opposite direction of the wheel that is gripping. Try it sometime.
Next the suspension bushings can do the same thing. They flex. It's ok under even power loads, but as soon as one flexes more than the other the same problem that was there with the subframe is now there with the bushings.
Even a properly designed suspension and steering system won't fix improperly offset wheels however. When the offset of the wheels is incorrect each wheel will produce a net torque about the hub axis ... this only puts strain on the steering componants during normal forward accelleration, but when there is uneven load on the front wheels one wheel will produce a net torque in one direction that is greater than the normally ballenced net torque of the other wheel. Thus causing the difference to be picked up by the steering componants, and your arms.
ylee you may consider taking a picture of the 9000's undercarriage sometime. I've never seen it, so I'm not sure if the subframe is a possible culprit. But check very carefully all bushings (including tie rod ends, which if worn can cause a similar effect), and look up your offset, measure it if nothing else seems to be wrong. If you cannot find anything wrong at all (and all the other usual suspects such as allignment have been taken care of) there may just be some amount of incorrectable flex in the frame of the 9000. But ... since I've never heard of that problem before it's likely just some worn out or miss-alligned parts someplace.
Dubbya~