2003 Ford Focus 02 sensor stuck on lean

Have a dtc 2274 02 sensor bank 1 sensor 3 stuck on lean. The motor really cuts out when you turn on ac or the defrosters I understand when you turn on defrosters the ac takes the humidity out of air. I have had this problem for awhile now. It still cuts out at other times but not nearly as bad, I thought when you turn on the ac isn't something suppose to step the idle up like the idle control valve. And the other funny thing about this zx3 focus 2.3 Litre motor there is no place to hook up a fuel pressure gauge no place I have looked believe me. So is there something that suppose to step RPM's up when you turn on AC or Defrost Cycle.