question about air/fuel gauge reading

[sxslut]

Hey.. I just installed an auto meter a/f gauge in my red top powered 240sx and I am getting some strange readings. When the car is at idle it is on the richest indicator light and when it starts to boost even under 1/2 throttle the light goes all the way through the range and disappears off the other side as if I was running very lean. I am pretty sure there is no way I am running that lean because I am only boosting at 11 psi and I have a large fmic, full 3" exhaust, megan manifold, gt28r, and 255lph walbro fuel pump. I have had the car running like this for several weeks now and it pulls very strong with no hesitation. I also pulled the plugs and they were perfectly intact and were colored like #14 on the chart of this sight: http://www.dansmc.com/Spark_Pl....html

So does it sound like i could be running lean, i have a faulty gauge, or my O2 sensor has gone to ****?