This is usually because of low RPM's, the AI usually start off slow and a little bit off the ground so they stall the engine. This happens a lot with manual cars, the AI even struggle with base game cars. This can be fixed by increasing RPM or adjusting gear ratios, whilst an inconvenience for the player it helps the AI greatly.
Sick mod, would love to see you add rear toe adjustment. I noticed it missing while i was working on a setup.
