Have you had a CT scan of your sinuses? I had one plus a brain MRI to rule out a sinus issue or a brain tumor for this continued altered taste but everything came back clear. The dentist was sure my problem was lack of saliva since my eyes are also dry I tried both medications that increase saliva and neither of them helped with the taste issue or even seemed to provide more saliva. It sounds as if we are all going from doctor to doctor to find an answer but none of them as one!!!