To do that you’d need to avoid it for a while and carefully introduce a small amount and see if you experience any symptoms over the next 2-3 days, while not introducing any other foods. If you’re suffering from die-off and other adjustments to the diet, it’s going to be difficult to pinpoint what’s causing symptoms. It’s better to leave questionable foods for testing until you’re largely in control of your condition.
A lot of the soy products you might be wanting to try are trash as well. That’s what Able was hinting at in the other thread. If you could find some traditionally produced tofu or tempeh, they’d probably be the best options.