Dear mikemac -
Since you have a serious allergy, sounds like maybe a "true allergy" to sulfites, you should never try challenge testing without your doctor present. It's even more unusual than my sensitivity.
There's more than one kind of gluten. Have you tested for rye, barley and oats? Some people can eat one but not another. Oats are supposed to be gluten free, but some people can't eat them.
Have you read the news published about the new genetically modified wheat having a new type of gluten we can't digest? I haven't looked for it online, but it was published in "Bottom Line Magazine," which does have an online magazine. The recommendation is for people to go back to older types of wheat and foods like spelt and other grains.
In your case I would recommend http://www.learningtarget.com/nosulfites/index.htm, if you haven't already. I'm not recommending buying anything to to anybody, but I bought Rick's book for the tables, which most people don't need, but I needed to do calculations of amounts of sulfite in some of the meds I take. Most of the food information anyone with a sensitivity needs is in the FREE book online. I have a possibly life threatening reaction - tachycardia - so I need more information and have a science education to make use of it. All of the book except the tables is in the FREE online book! I check back now and then because he makes revisions often. This is the only website I have found that doesn't just copy what is available on dozens of other websites and has research to back it up.