hi as per the information provided by you the source of mucus is the stomach not the chest.
as per the history of gout
where the patient suffers form gastritis
the acidic pH of the stomach is irritating the gastric mucosa
and making him feel nauseated, causing emptying of the stomach every now and then.
antacids along with regular intake of water will help keeping the gastric pH to near neutral .
it will take a weeks time for the gastric irritation to go away ,
take care and keep the follow ups with your gastroenterologist.