Iíve never had a problem with FPS in rFactor but have experienced a micro-stuttering effect which seemed to increase with the number of cars on the track and at certain points on the track. For example, there were a couple of corners at the Salzburgring race today that I could barely navigate because of the stuttering.
Anyway, after scouring the internet and trying all the suggestions, I finally found the solution to my problem!!! ...Wombatís nVidia FPS Fix
After dropping this d3d9.dll file in my rFactor folder, my stutters have completely vanished!
If youíre having any issues with FPS or stuttering, I suggest that you give it a try. Judging from the comments, it looks like ATI owners are having some success with it as well.