I don't believe diet was a factor for me. At least 15 years prior, I started eating only organic, was gluten free and really didn't indulge much in "junk food" (or alcohol). Aside from severe workplace stress (and recovering from childhood PTSD), my SIBO is due to impaired motility stemming from withdrawal from an SNRI; this particular SNRI was the subject of many lawsuits due to a sometimes deadly withdrawal syndrome.
Most of the neurotransmitters reside in the gut and various forms of 5-HT (serotonin) are responsible for aspects of gut functionality (including motility). It's interesting to note a Gastroenterologist I saw when I was first diagnosed (by a Naturopath) told me that a significant number of his patients suffer gastrointestinal issues while either on antidepressants or from withdrawal. In any case...
I've benefitted a bit from protocols and recommendations by Dr Siebecker, (leading SIBO physician and researcher); Dr Pimentel, and others; based on their websites, podcasts, papers, etc. I worked with a Naturopath initially and then a Functional Nutritionist years back. Only over the last 6 months or so was the motility issue broached when I started seeing a Gastroenterology specialist (for symptoms that seemed atypical of SIBO but I suspect are related).
It's quite unfortunate if not tragic for some of us, that most of "mainstream" medicine is not informed about the latest SIBO research (done by Dr Pimentel and his team at Cedars Sinai); I've gotten (bad) advice ranging from take laxatives and PPIs and probiotic strains known to feed methane SIBO. They advertised "SIBO Practitioner" but are sorely ignorant about not only the complexities/types but the actual research on this condition.