Well, let me see if I can give you a short version (but it will probably be long).

Newt is a little over 1 year old. He only ways 8pds, is a very picky eater, but has never been sick. When we moved he had no problem adjusting, immediately began checking out the house upon arrival. For the first month we were there June - July he has had no problems. The only food related problem he has ever had is stuffing his face with wet food and throwing up. We took him off wet except 1 or 2 times a week and he has been fine, no vomit.
In July my wife and I got married and went on our honeymoon. Having just moved to a new town we had no one to watch Newt so we boarded him at a Cat Clinic with special "Kitty Condos". He was in perfect health when we boarded him. They were big cabinets with windows. During his stay he got a little cold (runny nose). Vet prescribed Clavamox and anihistimine. His weight was 7.5 pds.
After a week he was well, but his nose became stuffed. We continued clavamox and anihistimine. During this time he was breathing out of his mouth all the time and not eating. We took him in several times for sub-q fluids. He was still losing weight (7pds)
A week later they switched him to Zithromax. He now has a drippy eye as well so they gave him a solution for the eye and suggested L-Lysine. A week later he lost 1 pd (6.5 pds) and we switched vets.
Vet2 prescribed interferon and some blood tests. Blood tests showed elevated protein and slight anemia (23% on test). She redid the test because she didn't think she had enough blood and the anemia came back as (27% on the test)...better but not perfect. After a week of interferon he was eating somewhat on his own but still breathing through his mouth. We took hin in the shower and his nose opened up. Vet2 wanted to put him on steroids with no additional testing so we switched vets again. He was still losing weight (6pds). We put him on appetite stimulant for a week, he ate and gained an ounce or two but soon lost interest in his food. He can smell it but just starts scratching the floor (his sign for I want something else).
Vet3 ran another blood panel for FIP and Coronavirus and took X-rays. X-rays showed no blockage and no fluid buildup. Blood tests started coming back yesterday, showed slight jaundice, low sodium chloride and his anemia is (30% on test) which means its getting less anemic. He is now at 5.5 pds.
Today, he still has a little gurgle in his nose when he breathes but does breathe through his nose 90% of the time. He is on no drugs and is being forcefed the following:
1000mg L-Lysine
1000mg Vitamin C
Energel (same as Nutri-cal)
Hills I/D or A/D (1/2 can)
All of that mixed together and fed via syringe:
24CC in morning
24CC in noon
24CC at night
I weighed him yesterday and concluded he has gained 3 to 5 ounces...hard to tell and the scale is different than the vets. We are keeping a log of his feeding and weight.