Strange sound

Wesely and sometimes Ice, the brothers in the signature, often sounds alsmots as if they have a breathing problem when I lift them up or hug them. It sounds exactly as the broncitis they always get when they have a cold.
When they are healthy I only hear it when I lift them or hug them and only once or twice.
It doesn't sound like a growl and it is definitely not purring. They are both real purr babies and purrs loud and personal.
I don't think it is a general breathing problem since they are full of energy, love to sleep under the cover where there is not a lot of air and I never hear it if I don't touch them.
Have anyone heard of something similar?

You need the vet to use a stethoscope on them... one of my girls has a chronic resp. problem, mostly with her nose, but when we go to the vet, they always also hear problems in her chest (she's lasted 14 yrs like this, because nothing cures it, only makes it go away temporarily, but don't assume your cats are like that, and do take them in).

They have been at the vet and are declared helthy. Since they both have had pnemonia both as very young (one week old) and once later in life they had a thorrow check up in December before they were neutered and there is no broncitis and nothing in there lungs. At least not in December - but this sound has been there as long as I've had them.

Well, it may just be a genetic thing, a little 'kink' maybe in their breathing tubes or something, obviously nothing to worry about.