Hi,
the AI need a "AI Line" for fast laps.
You can record it with strg+F6, start a free run, hit strg+F6, drive a CLEAN Lap and save it with strg+F7 after the finishline.
If you open the track folder there is after that a folder called "ai" he contains a ini file named "yourcarname.ini".
If you want copy and paste it, rename it to "default.ini" and you can race wich all car's...
...hope it helps...
Alex