I'm not a fan of some of the food intolerance tests, they're often a scattershot approach and can come up with a lot of false positives.

I think doing an elimination diet is a better bet. You can google that, or do what I do. Eliminate everything but meat and slowly add stuff in and wait to see how you react.

For me, my IBS issues are caused by: Nuts, chocolate, GLUTEN (the worst one), dairy (in excess), certain raw veggies.

Some of these I can eat in moderation, but not gluten. It is evil.

I think gluten is probably behind the vast majority of IBS, but if you're like me, you eliminate it and you're 90% better... then you gotta keep digging to find the other 10%.