There is some decent power to be had between 10.0 and 11.0. Most engines that I have worked on pick up 10-15 hp going from 11.0 to 12.0. What happens in that book isn't going to be the gospel. I have tuned a lot of engines and even at 1400whp running it lean isn't the way to go. The general target of 11.3 to 11.5 is fine for 90% of what is out there. If you run them too rich you run the chance of getting fuel down in the ring land and that can cause piston failure. Don't spend to much time looking at it. Tune the engine to a reasonable AFR and don't get greedy with timing.