Regarding MTHFR/CBS, the following thread has some resources that might be helpful to you and/or your doctor(s):/www.healingwell.com/community/default.aspx?f=30&m=3955750
Also, I was just reading the comments on the following page and a couple of them cite some disagreement with Dr. Yasko on one or two points:/drjockers.com/cbs-mutation-low-sulfur-diet
The commenters (not doctors or healthcare providers, as far as I can tell) mention Dr. Ben Lynch as another resource. In the second link above, there is an embedded YouTube video by Dr. Ben Lynch. So, perhaps that will prove informative, too. I haven't watched it.
Finally, the Dr. Yasko resources I shared in the first link above originated from forum member Georgia Hunter. In that link, you will see some of his comments that I included. I would weigh his actual experience against those commenters from the second link above. I'm not saying that anyone is either "all right" or "all wrong." Rather, most things aren't so black-and-white. Not everything works for everyone. And, what works for one today might stop working next week, next month, or next year.
Good luck in your endeavors,