My husband and I both did the genetic testing and the full Yasko protocol, including all the (insanely expensive) testing and supplements and the result was...drumroll...nothing. No change whatsoever. In fact, many of our test results were the exact opposite of what she claimed would be the case based on our SNPs, which led me to believe that a lot of her assertions pretty bogus. Same was true for my husband, so I can't say that it's because I'm a weirdo.
I do believe that supporting the methylation cycle is important, but I wouldn't worry too much about avoiding sulphur foods or ammonia. I'm not sure if you're asking just out of curiosity, or if you are actively involved in a methylation protocol and are considering a Yasko-type approach - Heartfixer is very much in line with Yasko. Either way, I'd recommend focusing on methylfolate and sublingual B12 (methycobalamin) and any of the other methylation supporting supplements that you feel are important, starting with really small doses and working your way up, if you can't tolerate them at first. I personally had no issue starting with regular doses of these, but my husband (who is an overmethylator) couldn't tolerate regular doses of methylfolate at first, so he had to slowly work his way up and now he can take it without problem. He also has no problem with MethylB12, but can't tolerate P5P. I actually think focusing on B vitamins is probably the most important take away I got from the whole methylation thing.
(Just as one example, my SNPs indicate that my ammonia should be way too high. I had it tested both through a blood test -which showed my ammonia was perfectly in range - and also I used those pee-sticks to test ammonia in the urine - which also showed my ammonia was perfectly in range. My levels remained good whether I was testing during my 2 weeks of no-suphur/no meat diet or whether I tested after eating a huge amount of sulphur (eggs, onions, meat, cabbage, etc...) And in fact, after doing the elimination diet, I can say that I do not react poorly to sulphur foods at all, regardless of whatever my SNPs are, and neither does my husband.
If I could only go back in time and tell myself not to waste all that money on Yasko's protocol...but then, at least I know I've left no stone unturned.