Johnny,
if you get a chance, pickup the latest issue (February 2001) of Chevy High Performance magazine. It has a section devoted to octane and HP. It also has a section on how to beat the detonation game.
I think you will enjoy the articles and it will probably help you with your problem.
Just so you can spot it easier, it has a picture of a red 57 Chevy and woman with a gas hose.
Later,
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Mike
1985 Chevy C-10
Mike's 73-87 Chevy Pickup Site