I'm currently building a ka24det and was researching an approximation of how much boost made how much horsepower. I found this thread very helpful so I thought I'd put it all together into a chart and make an equation for how much boost results in how much horsepower as seen on the chart.
If you plug in your desired boost for x in the equation you will get an estimate of how much horsepower your engine your will make, y. Of course there are many variations in power due to other mods but this will give you a pretty good idea of what kind of boost to shoot for in order to reach your horsepower goals.