Is it possible to recompile a customized the Darwin Kernel (or however it's called)? I just recompiled a Debian Kernel and realized how much junk I don't use and thought the same for OS X.

I know it's made for the hardware arleady but I'm sure if I removed some stuff I could squeeze a little more out of my iBook. I'm sure there's newer things installed that this mac doesn't have or something.