I should have clarified that a bit...rich for rich's sake doesn't create power, you're trying give the engine just enough fuel so it can support its compression ratio and timing.

The combustion of the gasoline isn't what creates the power...it's the oxygen that is atomized with it.

Here's an article on the system that we're just starting to use.

http://www.carcraft.com/techarticles/116_0402_tune/

In short, a dynamometer and a wideband O2 sensor are invaluable for tuning. But, as an aside, our SUs when tuned by ear and smell came out with very respectable a/f ratios on a chassis dyno.