All I can tell you is that I can't get anywhere near them... even derivatives. One serving of something like salad dressing with msg, or fast food (seems like almost ALL fast food has msg); and my pain level is up for literally a week. Not worth it. Add to that when you eat something like msg it sets off conditions to crave it! I have big trouble staying away from kens italian dressing, which is loaded with msg, but if I even see a bottle of it my mouth starts to water. MSG is pretty evil stuff.
How do we know what info to trust?
Trial and error. Keeping a log.
It's unique to each of us, so the only way to know is to do elimination diets. This is rough because sometimes we eliminate things that are coupled with other things and don't need to, like say... cereal and milk. Maybe it's cereal causing the issue and maybe it's milk, so it's a painstaking process.
good luck with this! Luckily there are apps these days that list lots of such things, which helps when we are out.

Great advice from Nina. Goodluck.

Thanks for the info, I was just hoping it would not come to this ( I love my diet coke) But I guess thats the way it goes from now on.