I use 92511 - I enter via the nasal canal and always examine the nasopharynx as well and dictate as such, so I figure that's what I should use.
As an aside, we have had private insurers not want to pay for follow up scope exams in patients that are NED. We have had to submit additional codes like dysphagia, hoarseness, etc and delineate those symptoms specifically in the impression/plan part of our notes in order for the follow up scope to be paid for. Ridiculous. If I have a completely asymptomatic patient s/p XRT for a head and neck malignancy some insurers won't pay for the follow up scopes. So dumb.