O2 sensor check connector and chirp noise
 

so i've been tuning my 85 gslse and it seems to be stuck rich. i don't know if my o2 is working properly or not but my boss asked me to try and find the 7-pin connector that is known as a o2 sensor check connector. its 3-wire in a seven pin connector according to the wiring diagram but we can't find it. anyone know where it is? also i've got a chriping noise when i rev the motor at idle or under load about 3k rpm. i've pulled the one drive belt i have on the car and the noise improved but is still present when snaping the thottle. anyone had this?