I just searched these symptoms and yet, my muscle stiffness and soreness pain was always equal, as in both legs, both feet and in my lower back. The classic fibro tender spots within the body I never seemed to have.@spinningmytires - I doubt that what you're describing has a clear relationship to fibro; it's got very clear correlations to a number of neurological processing disorders, as you've rightly pointed out. I'm curious - is there any connection that your doctors have discussed with you between your specific kinds of processing difficulties, and something like complex regional pain syndrome?
Then too, these symptoms would always come and go, according any unusual excessive physical activity. Then for several hours after such an excessive activity I would be suffering from extreme muscle stiffness and often a burning and tingling sensation in my legs. Other muscles were less affected. Sometimes the soles of my feet would be so painful that I could hardly walk. When I was stressed or when lacking sleep it would worsen. But other than the painful muscle stiffness and burning sensations these other symptoms aren't similar to my own experience.
And no, this has never been discussed with my doctors. Years ago, my PCP was always telling me that I shouldn't be having these symptoms. He also said that if he hadn't known better he would say I had lupus, though he said he knew that I didn't.