Help for chronic stuffiness

My cat Willis age almost 11 has had a stuffed nose with sneezing for over a year. Things my vet has tried on him are convenia, baytril, lysine, culture that revealed mycoplasma felis, treated with doxycycline, xray, nasal flush, cytologic evaluation of flushed nasal tissue, I think that's it I can't even remember all of it. The meds had no effect, xray was clear, cytology negative for anything suspicious. So here I am with a vet who says she has tried everything she can and a cat who is still stuffed up and sneezing after a year. He doesn't have a temp, he eats, drinks, plays, acts normally except is obviously irritated by not being able to breathe properly through his nose. I just spent about $2000 on diagnostics on my cat with colon inflammation, all of which were inconclusive and she has started the pred that I originally intended to put her on before I got talked into all the diagnostics.

In the end I will likely go the same route of advanced diagnostics for Willis and his sinus problems, but in the meantime, has anyone had similar problems with a cat and has anyone had success in treating sinus inflammation with steroid? It occurred to me while dipping into a 1000 count bottle of prednisolone to medicate Vivian for colon inflammation that the answer to Willis' chronic sinus troubles could be staring me right in the eye.

My cat Pheobe has been on and off prednisolone for years for chronic sneezing and sniffling. She was so miserable she couldn't breath through her nose so I took her to a specialist for a rhinoscopy and $1500 later they couldn't find anything specific. The specialist recommended trying steriods as a last ditch effort to get her some relief and it worked. She's been off the pred for awhile now but anytime she has a flare up I start her back on it.

I emailed my vet to update her on my cat Vivian who just started prednisolone for her colon inflammation/thickening and resulting weight loss and loose stool - improvement noted! At the same time I asked about trying some pred for Willis, who has been stuffed up for over a year despite many measures taken. I have a feeling she won't be in favor of it since she already told me she can't think of anything else to do and that maybe it's time to bring in the big guns. But I really want to give pred a try. At what dose did you treat your stuffy kitty Pheobe and for how long and how did you taper?

thanks

My cat Munchie has dealt with this, what worked for him was a sedated sinus flush (took 2 liters of fluid to get all the crap out), then we put him on Zithromycin 1 time daily for 5 days then every 3 days for 2-3 months.  We had tried EVERYTHING before that and this was on the recommendation of an internal medicine specialist.  It worked for him and he hasn't had any more problems with it.  He was constantly stuffy and constantly blowing green snot all over the place.  It has been about a year since his flush.

I can't remember the exact dose when she first started it. She's about 13lbs and I think she took 5mg twice a day for a week then 5mg once a day for a week then 5mg every other day for 3 months. At that time I weened her totally off for a couple of months and when the stuffiness came back I restarted. She was on and off it for awhile but it's been a long time since I needed it. I think all Pheobes uri symptoms over the years are from herpes virus. Now instead of sneezing and being stuffy she gets corneal ulcers and eosiniphilic keratitis. I really hope your vet lets you give pred a try, I know how hard it is to watch your baby have trouble breathing and have nothing you try help.