The AI is better in some car/track combos than others generally in PC2, turn1 is always where it gets messy, once you are past that they're not all that bad. The good thing is they aren't perfect drivers, they can outbrake themselves, lock wheels and spin off, you can tweak the aggression and skill levels to suit your tastes and see what works best. If you want a real test, turn the skill up to 120%...in the junior categories you might need to do that as the overall skill levels are scaled to the car class in career mode...you will also find if you start at the back, you can make it quickly through the pack and it gradually gets harder, the AI gets better/faster toward the front...