I have about 100 fps or so but in the race I get a hitch or two per lap. It already happened to me with Pc2 too, especially when there was some impact of the AI. it can be fixed? Or is it an intrinsic graphics engine bug?
I have the same occasional stutter, could not relate to impact with AI. Annoying. GamerMuscle says in the video below there's a way of capping fps to prevent this. I haven't got the time to try.
I have occasional stutter too - screen freezes for 1s, then sort of fast forward to make up for that. Not related to AI for sure, as it happens in MP with no AI. Got to a point where it was happening very often, then I did a files integrity check once, didn't help. However, without any further action it stopped happening for now.
Put "-fpscap xx" into your Steam launch parameters for AMS2 where xx is the limit of fps (minus 7% so).