I would get him to a vet asap. RI's don't go away on their own (if that is indeed what it is). Another symptom, besides the weezing, is spending long periods of time with the head elevated (draining fluid). Also, excessive yawning, and holding the mouth open to breathe. Even if you don't notice any other signs right away, I would get the snake in so that it doesn't progress any further. Snakes can die from drowning on the fluid that collects in their lungs, which occurs with an RI and personally, I wouldn't take any chance on that. While you are waiting to take him/her to the vet, raise the humidity in the enclosure to around 70% and also raise the temp on the hot side to around 94. I know that some people will tell you to lower humidity, but this only masks symptoms by drying up the mucus instead of breaking it up. The higher humidity will help to break up the flem and help your snake breathe easier. Hope this helps.