@Calvyn White One thing that solved most of my original issues I had with rF2 a few months back (intermittent stutters, lags and slowdowns) was to start it with high priority. Just put +highprio into the launch options fields for both single player and multiplayer (and don't forget to click save for both):
This worked wonders for me - I basically couldn't even race in rF2 without it, it was always stuttering and lagging. Not sure why rF2 is pretty much the only game I ever had to run with high priority, but that's rF2 for you I guess.
If it doesn't do anything for you, then obviously just remove it again (and again don't forget to save the empty field, which is kinda counterintuitive).
Also, in regards to slowdowns and FFB dropping out, you might try another possible tweak - in your controller.json file (in your rF2 folder under "\User Data\player\), there should be a "Use thread" line, set to either true or false (might vary on different setups). You might want to try to invert the setting - so set to "false" if it was "true" or to "true" if it was "false". This option sets whether or not the FFB calculations run in their own thread or not - some setups can have FFB and performance related issues if they do use their own thread, some if they don't, so it's worth testing. If it doesn't work for you, then just change it back to how it was, of course.