One of the side effects of Valium is it can cause weak or shallow breathing. It usually doesn't bother most people but it does affect some.
http://www.drugs.com/valium.html

There are a few articles if you google, I'm not very good at it but our expert is ill, so here is one,
I would tell your doctor about it.

I don't know about the diazapam but hydrocodone is a respiratory depressant and can cause problems for patients with lung problems. I was sent home with some after abdominal surgery this year and I could not breath well at all. Breathing returned to normal after I quit the pain med. Perhaps ask your doctor for a different pain medication?

i've taken/take both of those meds and neither caused me to have "junk in my airways"
i am assuming that is meant as Mucous/Flem in your airways?

some inhalers have a side effect of that. my once a day/long acting inhaler has a side effect that feels like i have a lump in my throat that i just can't seem to get up...so did your dr give you any different inhalers that may be contributing to the problem?

as for respiratory depressant; my dr worked with me & found ones that did not seem to slow my respiration rate any. as jazzkeys pointed out that is a side effect that usually doesn't bother people.
there is a flip to that coin also as with advanced COPD people can get a raised respiration rate & sometimes it is necessary to slow it down(from what i have heard; i have not experienced that yet).

ya i think there is more 2 it,i saw the lung spec and he said they shoulnd act like that,it maby somthing to do with my panic attacks and that i havent been exersising,when i go on my exercycle it seems to really help the bad breathing,well its time to get back into exersising ,and it looks like i might be doing the 18month new drug test if i qualfy,im motivated to improve,have too many thinks i wanna do,i restore old bicycles as my hobby,my goal is to ride them again as i did a year ago

Both drugs are central nervous system depressants and can cause shallow breathing, though it's not usually enough so you'd notice it in healthy lung'd individuals. Perhaps your sis isn't as advanced in her illness or of course there is the fact that some people just produce more phlegm than others so it wouldn't be an issue for them. Also opiods in particular are cough suppressants so having your natural urge to cough supressed when your lungs are filling up with crud puts you behind the 8-ball when it wears off. Maybe try that stuff that people take to break up phlegm if you're not already taking it....mucinex I believe it's called.