Engine PCM 99 f250 7.3l 6spd

[A-Chay-47]

I had a check engine light on for the longest time for a bunch of automatic tranny codes and I have the 6spd.. Dealership told me someone replaced my computer with a PCM from a automatic with California emissions. Does anyone have or know where I can get one that belongs in my truck??! Also would this California emissions crap have something to do with my poor fuel economy compared to one with out it? I'm getting 13-15 mpg with cold air intake 4inch straight pipe turbo back and hyperpac stage 3 programmer