IMO The temps(on the warm side) should generally be at 90 degrees all the time.
You mentioned some leftover shed on his head. It could be possible that there's some shed left around the nostrils that's causing the sounds. Does he have any other signs of RI? Any mucous or bubbles around the mouth area?

If you haven't previously had your snake in for a general check-up by a good reptile vet, it wouldn't hurt to do so now. Atleast that would answer your assumption of an RI problem. Good luck.