Perfect Dark wasn't running badly for me, when I didn't even have this nickname, all the way back in 2002, when a 1.3 Ghz single core processor was something to brag about.
I definitely seem like an old fart, LOL.
So, I'm surprised it's laggy, in an era where processors are faster per clock and 3.5 Ghz is the norm!
Thus, I suggest the counter factor be set to 2 and if still jerky, try 1.