Presumably they're using a checkpoint marker system? I found that on the straights it pays to have them look a long way ahead for the target marker so they don't weave left and right as they get too close to a marker. As they slow for corners they look a bit closer.
They usually do, unless they are "Watching" something else, or are close to a wall.
Actually, the problems solved now. It was, as said, caused by the tuning of the AI to the tuning of the cars :). It caused them to always oversteer basically.
Good tips there though for others, though i already use them along with more advanced techniques :D
Thanks for your comments.