@Dan, does GABA help you now? I remember you tried both Twinlab GABA-Plus and self-mix GABA+Inositol+Nicin. Did they give you the same effect ?
GABA-Plus has diminished effect with me too. I recently received headache if I took GABA Plus the night before and I've bought some "pure" GABA, Inositol and Niacin so that I could test to find out whether it was GABA or Inositol that gave me the headache.
I finished a few days of low dose 5HTP and its help sleep quality but have no positive effect on, and likely have tuned down, my sensation.
I bought some Lecithin and Arginine and will later take them with Choline and B5.