So just pulled it now and after discovering an extremely disgusting rodent nest underneath it I noticed this plug was bent so after straightening it out I took this picture.

What's its purpose and is it important?

 

that looks like an air temp sender and no it is not mounted into the LIM on stock FC,s
it is usually mounted into the top hat for the TB
the inlet air temp sender is however part of the hot start sequence flags
and if faulty can amount to the car doing the incorrect start sequence

 

On an S5 NA, the IAT sensor is threaded into the rear-most intake runner on the bottom section of the UIM. (which is what that picture appears to be of)

On an S4 NA, the IAT sensor is threaded into the plenum.

On all turbo models, it's on the cover piece attached to the TB as bumpstart mentioned.

The IAT sensor is used for fuel corrections while the engine is running based on air temp. The water temp sensor on the back side of the water pump is actually what is used for startup fuel calculations: https://www.rx7club.com/showpost.php...83&postcount=2

 

ah, s5 NA ! duh !

the AIT is used as a flag to to determine a warm start correction on s4 upwards
( as well as being used full time by the ecu to determine fuel corrections due to air inlet temps effect on air density )

when AIT is over 78 C ( 172 F ) AND coolant temp is over 65 C ( 149 F )
warm start will be enabled and the pressure control solenoid bypass engine vacuum to the fuel reg for 120 seconds
this is an anti perculation strategy

note the lesser spec ( euro and south america ) versions have different flag set points and a shorter 90 second strategy of fuel reg pressure control bypass
( 50 C for AIT and 65 C for coolant )