2003 Ford Focus cutting out when idles

I have posted this problem before.It had a dtc 302 and 2274, well I exchanged coils 2 and 3 and reset the computer,and now it does't show any misfire,just the 2274 bank 1 02 sensor 3 is stuck on lean,it does't stall it just cuts out at idle only.So I was thing stuck egr it does't act like a vacuum leak,but I don't know how these new cars act with a vacuum leak,I know older vehicles when they had a vacuum leak you sometimes could hear the whistling or you could tell buy the way the motor was loping,that is why I say it does't act like a vacuum leak.Does anybody have any theory on this.And does anybody know how many volts a coil on plug should put out?