I'm guessing you're referring to Amy Yasko's claim that those with CBS polymorphisms should avoid sulfur, sulfite, and even sulfate.
This general information has been proven to not be true. Check out the Phoenix Rising CFS/ME forums for more information. Even Yasko has changed her mind on one of the CBS genes, and Ben Lynch has found that some of them are indeed DOWNregulated, not upregulated.
If you have proof or clinical studies or references from PubMed that prove otherwise, I'd really appreciate seeing them.