Just raced the GTR3 rF2 pack on VIR. AI seems to be all over the place, except for the track. While the MR18 is just fine.
Are you using the latest update? The AI should be working properly now. A game files integrity check just to be sure might be worthy. Also its worth a mention that not all the s397 GT3 car AI are working very well... like the Mercedes (is really quite off), Corvette and Radical show some poor behavior under some conditions.
Your ultimate racing experence against the AI is when the AIW (fast path) was made using the same car make your using
This seems not to be the cases in my experience. For sure different car types benefit from slightly different driving lines but this is a minor effect imo.
Other than mod cars how can you bring an s397 GT3 car into DEVMODE ? I doesn't seem to work and crashes rF2.
When you see bad AI behavior like going wide it could be a corridor issue, but in many cases I found that I needed to make tiny tweaks in the fast line manually to get the AI to act as i wanted. This AI problem was most noticeable in short radius corners (hairpins) or chicanes where the car velocity needed to slow from the first to second apex.
rFactor 2 AI has some nice features and the editor is much improved over rF1. That said the AI in general needs more work.
The braking is not very nice (constant tapping of the brakes in medium or cornering brake zones) where some s397 GT3 cars get into this cycle of on throttle, then on brake leaving short skid marks on the track in the brake zone. Also as noted, for some reason the cornering speed calculations are off in some cases and the cars push wide, lift on the throttle, correct to return to the fast line, and continue... all the while loosing a lot of time.
Cheers