Help or hindrance: do IgG tests throw us off track?

Are IgG tests really the be-all-and-end-all of intolerance testing or can they take us completely off our healing track. My own experiences suggested the latter so I began to formulate a theory why this had happened...and then I read the very same theory from someone whose opinions I respect mightily - Anthony William, the Medical Medium. Here's the conclusion I've reached about the pitfalls of IgG and how, or whether, we should use (or even avoid) them.