Rapid wheezing in a cat.

My family adopted a cat from the humane society almost a year ago. When we got her she was just finishing up her last dose of medicine for an URI. Once we took her home everything has been fine and she had no signs of a remaining URI. We took her to the vet and everything checked out good. She walks funny (with a hobble) and the vet believed that she got hit by a car but has no remaining pain from it. She does have a wheezing/snoring sound that she makes at times when she breathes in. It doesn't sound painful, but I'm sure it's annoying for her. I have noticed that she would go through phases of breathing rapid shallow breaths. Everything that I look up on the internet points to something wrong. Other times though, she breathes just fine. She acts just like a normal cat. She plays, eats, drinks, and goes to the bathroom normal. Lately though she has been having more episodes of this rapid shallow breathing and will be purring for hours, which I know can be a sign that something is wrong. It seems like these episodes come at night and even when she is sleeping her breathing is abnormal. I also noticed that when she is having this abnormal breathing she curls up into a ball and resituates herself in that position many many times.