RE: problems with rs4
I had the same problem with mine. At low speed it would go straight and the faster it went the more it would pull left.
I ended up taking the front and rear diffs apart and relubing them. This ended up working, but I am not sure if it was the diff work that fixed it or just taking the whole car apart that solved the problem.
One simple suggestion is to make sure that none of your wheel nuts are too tight. This can cause some binding on the wheel.
Good luck.