I have been turning a few laps on Road Atlanta. I lowered the AIBreakingStiffness to (0.9,0.9,0.8). Just so the Ai wouldn't brake so perfectly that I couldn't keep up. Over an eighteen-lap race, If I am friendly to the tires, I can catch the front AI as their tires get soft at the end of the race. The AI set is pretty tame, so there is reduced erratic swerving and bumping with settings like the following.
AI to AI Collision Rate =18
AI Min Radius=0.10000
AI Max Load=32000
slowwhenpushed=0.04
AIDraftstickiness=0.98
AIMinPassesPerTick=2
AITorqueStab=1.2,1.25,1.00
Your fine-tuning on the Drygrip Values is having a more significant effect than I thought it would.