I went through similar exhaustive testing in Denver at National Jewish. There have been other threads here on this issue. I also tried laryngeal blocks that were not helpful. Currently I take 35 mg amitriptyline at night. It usually works for 2-3 months, then I switch to tramadol twice daily when the amitriptyline stops working. Switching back and forth with these meds seems to work pretty well for me. It keeps me about 80% cough free. I recommend you work with your ENT to try different solutions. My ENT calls us his chronic coughers. You are definitely not alone in this!