My partner has IBS, so I'm also frustrated with unidentified food reactions/digestive issues. But I can't help her by ignoring the best tool for discerning reality we have, which remains scientific research. The results on MSG, glutamates, is very, very clear.

"You think the probability that someone on the planet has a sensitivity to a certain food/molecule is about the same as there being a teapot orbiting Mars?"

No, I KNOW people have food sensitivities. But not to MSG or its metabolites. I have as much evidence for the teapot as the MSG sensitivity, so I couldn't really guess which is more likely. I'd be happy to change my mind on either if presented with plausible research!