I tend to have the same issue with FPS loss. I ran SPM while running around through thick grass.
Image has my specs. My VRAM seems fine so no idea why I keep getting these huge FPS spikes down to 2-4 fps. I also know the temp on the SPM is incorrect as my system temp gauge has much lower temps.
Anyhow wish I could be of more help. Nvidia driver is 326.41. I have a lot of HR textures, tons of grass mods, and HG ENB settings. My ini settings are pretty vanilla though - just the ones you need for ENBs.
EDIT: In case it is of any interest I did the exact same save and run I did before - didn't change anything except use the 201 dll and 201 enbhost file.