Does the "custom ai parameters for track/car-class" work for you? Well..it kind of - for me. It works for 2-3 times - after i re-launch the game-, but after the 3rd or 4th time it seems to be deactivated again. Am i doing smth wrong?
for some reason rF2 seems to lose track of several settings. The golden rule for offline racing is to race one event and don't restart or skip sessions. Then exit and completely reload. I would even shut down your computer and restart that to clean out any left-over cache rF2 didn't clean up.