Any time there is a coating on the tongue, one should consider fungal or bacterial infections. Smoking cessation, while beneficial, won't clear up an infection. Strongly suggest consulting a Naturopathic or Integrative Physician for assistance with the tongue issue, as most main-stream MD's have no training in this.
And no, it's not likely related to the sulfite issue... I have no tongue coating, but definitely have a sulfite intolerance...
Chronic Lyme, Bart., Gluten & Sulfite Sensitivity, Many Food/Inhalant/Medication/Chemical Allergies & Intolerances, Asthma, Gut dysmotility & non-specific inflammation, Lupus, Osteoporosis, etc.; G-Tube
Meds: Flagyl, Domperidone, Zofran, Claritin, Andrographis & other herbs, homeopathy, supplements, etc.