I am an expert by no means, however i know a little. The ideal afr at idle is called stoichiometric and that occurs at 14.7:1. This is most efficient ratio for burning the cleanest. However that number changes big time when dealing with high performance. And please know that tubo/boosted cars differ drastically compared to naturally aspirated cars. At WOT with a boosted application your looking for 11.1-11.9 Afr. I was told by the guys at Anderson Ford when they see the air fuel ratio hit 12.0 they automatically shut it down to avoid any problems whatsoever with running lean now obviously 12.0 is not at dangerous levels yet but your heading in that direction. A naturally aspirated car can run in the 13.0 range and be perfectly fine.
14.1 under WOT would mean you need more fuel because your running lean. The first number represents parts of air. So in this case 14 parts of air for every 1 part of fuel. If you LEANED that ratio out you would get 15.1 or 16.1 and so on. By adding more fuel making the ratio more rich, the first number would go down, 13.1 or 11.1 and so on.
14.1 under WOT would mean you need more fuel because your running lean. The first number represents parts of air. So in this case 14 parts of air for every 1 part of fuel. If you LEANED that ratio out you would get 15.1 or 16.1 and so on. By adding more fuel making the ratio more rich, the first number would go down, 13.1 or 11.1 and so on.
At idle, the A/F ratio should be a stoichiometric 14.7:1 for best emissions. Under light throttle cruise, the A/F can be set leaner (15-16:1) for good fuel economy. At WOT, the A/F needs to be set rich on a turbo engine to prevent piston-melting detonation and 11.0-11.5:1 is considered safe.