Welcome to the site. Always nice to see new members.
Forget the high octane stuff. The 750 Vulcan was designed to work just fine on the low octane. Infact, the owners manual recommends the lower octane.
And instead of a gas drier additive, try to find some Seafoam. It's available at alot of auto supply stores anymore. It works wonders on getting the carbs cleaned out. A double or even triple shot (normal is 1 oz per gallon) wouldn't hurt. It's sometime called the 'miracle in a can' around here.
The popping on decel is kinda normal. I'm one of those that kinda like the Brrrr pop, pop, pop, Brrrrrr, pop, pop.
There are some carb adjustments that can help reduce it, or what's referred to as 'marbling'... adding a couple marbles to the lines to the coasters (the coasters direct unburned gas into the exhaust to reduce emissions)
The hose Cindy mentioned is also a common problem. It's a good idea to cut the end of the hose at an angle to stop it from bottoming out.
Also, how are the air filters? Dirty ones can cause issues.
AKA: Tim & 'The Adventure Cycle' VROC #24567, NEVROC, SteelCity VROC
"When life throws you curves,
Aim for the apex."