Hi David,
My experience may be too unrelated but I thought I'd share anyway. I have CRPS due to surgical nerve damage in my foot and share symptoms with the SFN gang. I have always been a little food reactive but noticed after getting CRPS that this tendency became much, much worse. Nightshades, spice, nitrates and wine can set off a flare of redness/hotness/discomfort (progressing to stinging if bad enough) that is worst in my affected foot but is also seen in my hands and unaffected foot.
CRPS has an auto-immune component in some patients. I really wanted to find out what was happening as I have a shellfish allergy and am prescribed an Epipen. The last thing I need to do is inadvertantly make myself worse. So I went to my allergist to make sure I wasn't headed down the anaphylaxis path with any exposure to offending foods. Lo and behold, scratch testing was completely negative! My allergist said that some people have a metabolic reaction to certain foods that fits exactly what I experience. He said it can be annoying but was not causing harm.
My ANA and sed rate were pretty much zilch. Between that and the negative allergy test I have decided to occasionally indulge in pizza without worry

.
I don't think identifiable triggers necessarily have to mean auto-immune. But I agree that keeping triggers down is a good thing and will help the system settle over all.
Hoping you find relief soon,