14.7:1 is stochiometric, which means that the amount of air and fuel match and you get complete/clean burns.
I will run my truck 5% lean (15.4:1) when cruising at light throttle. It has slightly higher NOx and lower power, but saves 5% fuel. You will be generating more heat running lean, but as long as you have sufficient capacity in your cooling stack it saves money.
You can get more power by running rich. That is the idea behind "rolling coal" and power enrich on throttle snap. Depending on who you ask, the peak power is around 13:1. I would recommend waiting to adjust that until you have it on the road and can experiment with it.
