First, "snuffles" is a relatively outdated term used to describe a set of symptoms, but not their cause. Has your vet told you what is actually wrong with your Gizzy? Has he been on any medications?
I would consult with your vet about it and take into account what you know to be normal and abnormal for your bun.
One of my rabbits, Fiona, sneezes all the time and always has. She's been medicated several times but nothing has solved our problem. A few months ago we found a lump on her that ended up being a cancerous mammary tumor. Even with her respiratory issues, she got through the surgery just fine.