Welcome to BHQ!
If your not riding in big puddles, ditch the air box and get some pod filters. An adjustable timing plate is a cheap mod, i would run +4. Porting is a great way to gain HP without spending a ton, I personally like Wildcard Racing for porting or any work on your banshee. With some motor mods you will HAVE too re-jet.
Don't run a boost bottle, they don't do anything for power. I like running Klotz R-50 at 40:1, but everyone is differant on oils and ratios.