None of my AI never EVER pit. they just run outta gas and die (a UF1000 could win on a 40lap race vs FV8's). Still as far as I'm concerned the grade should be selected via newbie / learner / pro / etc. If I wanted n00bs I'd select newbie. Sorry to say it, but this is a pointless thing. It took ages to get their confidence up to make a race of it. Sorry, pointless, End of.
Cheers, B