Sometimes my snakes will make faint puffing or whistling noises when they're moving around on my arm or straining to move over something. If I open their cages and they don't wanna be messed with they'll let out a little hiss. However, last year I did have one develop an RI when the power went out in a snow storm and neither I or my roommate were home to keep them warm. He never had any bubbling or drooling but his breathing was a little wheezy and kept getting louder and more frequent and he made popping noises. I took him to the vet and had him swabbed and sure enough he was sick. If the wheezing you're describing has shown a pattern of getting worse or louder I'd take him to a vet just to be safe even if there aren't any bubbles or drooling.
When you do go, demand an oral swab test. I had to go through a lot of supposed "reptile" vets before I found a reputable once who would do the swab and knew what they were talking about. If the snake is sick, they'll probably give you injectable antibiotics according to what bacteria is cultured. A lot of vets will just give you injectable baytril and won't do the swab but don't let that happen. Baytril may be the correct antibiotic that the bacteria type is susceptible to but you won't know that without a culture and injecting useless antibiotics will just make the situation worse.