its the same as putting a bunch of high performance parts on an engine that work against each other than together, example, say you have a real heavy car, put a full race cam thats designed for 4000 to 7500rpm's, 2800rpm tourque converter and a 272 gear in the rear, nothing here will make the max horsepower at the same time to the rear wheels, everything is basically working against each other, seen it time and time again while street racing, the stone stock car will smoke the car with all kinds of wasted dollars put in it, same as the high octane on a stock compression motor, just cause it makes one engine run better doesnt mean it makes all engines run better, engines need to have max cylinder pressure around 15deg after tdc, so therefore if you run a higher octane fuel on a stock motor the mcp will be after the 15deg it needs to be to get max hp, that means loss of power and nobody wants that.