Insi had similar problem since we got him. After $325 fees (x-rays, full blood lab test, the work), the vet said he will always remain like this and nothing we can do. I told him about Ziniquin (read the post here). After he finished his course, he is cured. NOTHING, NADA, ZILCH! No sneezing, coughing, nothing! He is still a heavy breather and he may get it back but for now, this is a magic drug! Thanks for the post :-)