Why too different intake air temp sensors post and pre face?

[Rob Furniss]

Camskill list two numbers for the air intake temp sensor:
MD182787 up to 12/1997
MD326170 after 12/1997

I've fitted one to my charger cooler/intake plenum but it wasn't the one that was originally on my car but was from a spare plenum.
When the car has warmed up and idling my AFR goes rich and i'm wondering if it could be due to this as camskill say:
'Air intake temperature sensor.
This gives the signal to the ECU for the intake air temperature and when faulty can be the cause of massive emmisions highs on GPX cars.
'
If i've fitted one that's sending the wrong signal to the ecu.
I'm going to try my old one and see if it makes a difference but was just interested why Mitsi would change it and if there really is a difference. My car is a facelift but late 1997.
EDIT:I've trimmed my emanage map for idle and improved it a bit but think there is an underlying problem and it's not the emanage's fault.
I also had a similar issue to this on the old car when I had a split vac pipe to the map sensor so was initially thinking this may be the cause as i'm pretty early on with this setup and need to check more things but know there could be multiple reasons and now have one more to investigate.

[Rob Furniss]

I've swapped with the spare sensor (which had same number stamped on it) and still same symptoms so may be something else.

[payaya]

Test the sensors out and see if they are reading right. Maybe trace the harness back to the ecu if you think it's IAT related and measure the voltage at ecu pin?

Bad mix when warm, you should also look at the temp sensor to ECU and oxygen sensor?