i noticed that too on my euro, i think its quite normal for it to want to tramline :]
recently had new tyres and alignment done - still there lol. havent had a service for a while but i highly doubt it will be the power steering

i keep mine at 37psi (michelin 16" pp2, stock rims no lowering). i noticed the left side was on 34/35 psi (front/rear) and the right side was on 36psi for both :S