In my case, not a bad computer, but I need to reinstall Windows when I have some time
But when i turn off the framelimiter, I can easy go over the 25 FPS, but.. when you have a frame drop from, lets say, 80 FPS to 70 FPS, it's a much bigger difference then the drop from 25 to 15 fps.
But still, not LVP related, this is GTA SA related (Not even SA-MP) so.. closing this "bug".