a/f meter O2 narrowband sensor location
 

i had a A/F meter lying around and want to hock it up in the 7 i need to put a bung in the exhaust but not sure of the best location
the Lambda sensor is just a 4 wire universal one with heater

Black = Signal [0.1 - 1.0 Volts]

Grey = Earth [0.1 Volts Max]

White = Heater [12 Volts]

White [ Heater 12 Volts]

the meter only takes 1 wire persume Black, so my question is
A) where is best to mount the sensor in the exhaust
B) do both white wires just hook up to 12v+ all the time the ign is on?

i know wideband is better but for now this is the set up maybe wideband in the future
thanks
Mark

A) on my car i welded the bung on the collector just after the 2 pipes come together on the header.

B) my sensor only had 1 wire so im not shure on that one.