Sadly, any game based on rFactor -- including GTR2 and AMS -- has AI oriented around road racing that has specific behaviour making oval racing weird. rF1 and GTR2 are particularly ill-suited. In AMS1, you CAN get a half-decent oval experience if the modder does a lot of careful tweaking (e.g. Patrick Giranthon's Fontana mod with CART Extreme) and even then it's hit-and-miss, and generally a subpar experience.
One idea: if they're staying two wide, it suggests the track is trying to use the 'stock car' AI rFactor had (but it was poor). In the track's AIW file, there should be a parameter to change it to 'road racing' mode, and counterintuitively it might give a better experience -- especially for Champ Cars and Indycars, which race in single file largely.