Look to your parents blood types. I'm pretty sure one of them is avoid for wheat. Your pH makes a big difference as well. My wife is B and unable to eat potatoes unless her pH is high. Her father is 0 and potatoes are avoid for him. Crazy stuff. :)

One of the biggest problems people have is they're not aware of what 'feeling good' is like. :) I recommend people stick to neutral and beneficial foods for a month, once the system is much cleaner, the effects of avoid foods are much greater, difficult to miss. :)
Here's the updated list from D'Adamo