You can get ( and see...of course ) Ai pit stops only if:
1) You set at 100% lenght the race
2) You assign as "default" set up for a track in a specific car class ( for example, F1 f2009 ) a setup including the right fuel quantity and the numbers of pits for that race
3) But...overall...You have to edit, first, Your PLR file is User data, opening it with Wordpad,
changing to "1" from "0" the strings with "fixed setup ", and AI fixed setup", in order to get for
player and AI driver the specific setup You assiogned to the track.
When You play, before to start qualifications and race, go in Setup mask....: make a specific setup for that track...at least with the number of pitstops, for example. Than, save, load ( for human player ), and Assign ( for AI drivers ) the new setup.
You will race, like Ai drivers, with specific fuel quantity for the laps You choose, and all drivers, with a sort of randomized times around the laps You set in setup, will make the pit.