I have the same problem. I have no difference at all before and after using TESVAL or SkyBoost.

I'm using a Dell XPS17 L702x, GT 555M 3GB, 8GB RAM, i7-2760QM 2.40GHz, 1600x900.
The point I'm using to check is at the top of Whiterun, looking at the tree (lol). I get 31-32 FPS always, independently of which mod I'm using or even if I'm using a mod or not. I will try the Afterburner that was recommended before now to see if something happens.
UPDATE: My GPU is working at its top... so I guess I'll have to play with my actual FPS rates

UPDATE 2: I don't know why I had the shadow detail at high, I set it on low and now I'm having 39-40 FPS at the same spot. I don't know if that happened because the shadow detail uses a lot of the GPU, because the mod is acting like a charm or both reasons... anyway, I'm really glad now
