I've seen a couple mentions that the most likely place for it is in the cecum (center of the small intestine) but I'm guessing it could be anywhere.
I suspect I've had it for at least 4 years, progressively getting worse all along. I had a colonoscopy a year ago and an upper endoscopy this year that went about a foot into my duodenum, and nothing unusual was noted by the doctor in either procedure. So I'm guessing that at the time I had it mainly in the center of the small intestines.
I did have some oral thrush when I started my diet to stop feeding it, and that has backed off quite a bit now, a couple months later.