Definitely a missing feature in some cases. Would of been nice if they at least put a final drive ratio option.
I took the Citroen rally car on the big ring test course and it very quickly tops out in 5th gear stuck at 150mph bouncing off the rev limiter with tons of speed left to spare while the AI cars EASLY cruised by me.
After trying several other cars, on this track above, it's definitely an issue.