As someone who has had experience w/polyps in cats, your vet may be able to just plain look in your cat's ears and throat w/out having to go through the expensive tests. I can tell you that, if s/he does have a polyp, it can slowly strangle her if it grows down into the throat. I don't want to appear negative and I'm not laying a guilt trip on you, just telling you that your vet may be able to see if there is indeed a polyp w/out the tests. As for what else to do, I've not had experience w/treating congestion on my own, so I can't help you there. Good luck.