If you have hi compression or more "timing advance" you'll need higher octane fuel.
Reason being, you're creating more heat, and need the fuel to actually burn SLOWER, or else you can get preignition/detonation (air/fuel starts to burn before the spark occurs) which leads to engine failure.
High performance engines create higher HP from using higher compression. The more you compress stuff, the more heat it creates. This is how a diesel engine is able to ignite the air/fuel without even using spark plugs. (strictly by compressing the air/fuel so much, it explodes)
Also as engine timing (spark) is advanced, it generates more heat.
LOW octane fuel is more explosive, and is why it will ignite before the spark occurs causing "preignition"
Higher octane fuel is slower to burn, therefor it shouldn't ignite until the spark occurs. (obviously this is a general statement) In extreme cases, even high octane pump gas can be made to preiginite. Hence the reason for 100 + octane fuels. (Most of us aren't using engines built for that in a buggy)
So, to answer your Q, you should run just enough octane to ward off preiginition in your engine.
Hope this helps.
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