What kind of air filter or intake are you using? I used to notice a dip in that same range in my wife's Outback (automatic), and it went away when I replaced the paper element panel filter with a high flow aftermarket filter. Something like a K&N or Amsoil filter should do it. I must admit, I didn't think the dip was that bad, but it was noticeable. All the other stuff sounds good too. Just another option.
Good luck, let us know what you find-