This is very much a sample size of 1 finding, but for me the biggest intervention was being put on broad-spectrum antibiotics to deal with an infection after some unrelated surgery. I was fully expecting the antibiotics to make things worse, but it did the opposite. It turns out there is a thing called SIBO (small intestine bacterial overgrowth) and it's likely I had that.
Over six years later and I've only had the rare IBS flare-up once or twice, and they don't last as long as they used to. It's been a huge improvement to my pain levels and quality of life.
Ask your doctor about SIBO.