I used to hear that one could add 'moth balls' to your fuel to increase octane; I still have a bag of them in the top of my old tool box.. (My nose reminds me every time I open that tool box)..
Another and very good method for *real* octane booster for unleaded fuel is to add 'real lead'...
It was available from several sources including...
http://www.wildbillscorvette.com/OctaneSupreme01a.htmhttp://www.jackpodellfuelinjections.com/I haven't purchased any of this in quite a while, but it's probably still available.. Just be careful when you are adding it to your fuel tank...