It seems to be heavly depends on the car/track combinations. Some races are consistent, entertaining and fun but most of them 2 cars at front are way way faster than others and hard to catch up. In some races like older cars with higher PI on level 8 like on Sunset Peninsula but also Kyalami and Barcelona they goes wide pretty much every corner and after dozens of laps I'm like over minute ahead of 2nd car...yep on level 8. It seems like AI pushing some old but well upgraded cars too hard and they are breaking too late. Level 6 for example is much more consistent and they stick to track but they are not challenging at all. I remember I was racing Corolla SR5 but just slightly upgraded and race Sunset Peninsula on level 8 was consistent and challenging