ATkins book has a few pages on yeast. I tried to find it online so I could link it for you but no luck, see if you can get hold of a copy of the New Diet Revolution (2002) and read it. But basically he says mould can also trigger reactions. In addition to the high sugar and grain foods, which you will already be avoiding, he list the following as possibly causing a reaction, and advises giving them up for 4-6 weeks and seeing if htere is any improvement. If not, it is not yeast. If it does improve, experiment by reintroducing them one at a time and seeing which ones affect you.
cheese (except mozzarella and cream cheese)
vinegar, soy sauce and other fermented condiments
peanuts, cashews & pistacchios (all nuts are prone to mould but these are the worst)
smoked or cured foods
beer, wine, spirits
yeast containing vitamins (read labels carefully)