I asked a vet about this once and he said you couldn't really tell by noses (unless they are dripping, of course). If I want to check for a fever on a cat that won't let me take its temperature, I feel its paw pads. If they are warm and damp, the cat has a fever.

Good luck on Honeybun. I sprint to the vet with my FIV+ boys too at the first sign of being off-colour. In fact, I spent about $85 (exam plus meds) a few weeks ago on Thumper just because he didn't want any breakfast. By that evening he was racing around playing again and he hadn't even had any of the meds yet.

I know that FIV+ cats often have mouth problems, but is it possible that Honeybun has a gastro problem? I know people can get bad breath for that reason.