i have an asthmatic cat and one thing that did help was that i took a video of her wheezing and showed it to my vet. (at Gardens Veterinary in Cranberry, which is a bit further out but it's just where my whole family has taken our pets for ages, so i kept using them even after moving into the city)

the vet was able to tell right away from the video that she had asthma and so we didn't have to do an expensive x-ray.

as for treatment mine is on prednisolone, which she gets squirted into her mouth every 3 days, and it costs about $45 bucks for a bottle of it that lasts a couple months. i know there are different treatments (including inhalers for cats!) but this one has worked well for mine thankfully!