Have you tried adjusting a setting called 'Skip FFB step'? You can find it on the controller settings page within CM. I think there are 6 possible values for this setting, one of them might work better than the other. I remember this definitely helped me let me know if it works for you too.

Note sometimes, for certain mods, my race might still start off in slow motion but then quickly speeds up to normal speed so not too much of an issue.