[Motorhead302]

Actually, octane makes fuel burn slower. Technically, if your car will run on 87 octane fuel without detonation, then it will make more power on 87 than 93. Or 104, or 110, and so on.
So, once you bump your timing, try running 89 first, and if it doesn't ping when you run it hard, you might even try running 87.
Just as an example, i had a friend with a '96 GT, and he put 93 octane gas in it with a bottle of 104 octane booster, and the car ran "like a pig" (his words). So, on the next tankfull, he put in 87, and he said that it ran like a raped ape. He suffered from the same misconception that a lot of people have that more octane equals more power, which i think usually stems from seeing wild drag cars running 114 octane gas and such, and thinking that that has something to do with making more power, when in reality they use such high octane to prevent detonation and engine damage due the high boost/compression/nitrous or whatever.
So anyway, bottom line, running more octane than you need to makes less power. Running less can cause detonation and damage. The key is to find out how much your car needs with the mods you have and run it.

Later,
Eric