The car:
Evo 7 JDM
3"TBE
AMS IC
Walbro 255
Delphi 120lph injectors (recently installed and fuel trims are within 2-3%)

I was at stand still in some light traffic when the engine check light came on. It went as soon as the car started rolling again but came back when standing still and when I parked. Not being able to check the code at that point, I checked the oil, coolant, MAP jack, MAF jack and the O2 jack. All seemed fine. Now that I've checked the code, its an "Intake Air Temperature Circuit" fault. To the best of my knowledge I don't have an air temperature sensor. The car works fine other wise other than being greedy on the gas since the injector change.

How should I start to diagnose this problem?

 

That circuit is part of the MAF sensor IIRC. I'd swap it with a buddys if you can and see if the issue goes away

 

Sounds like a plan. I'll try to recreate the problem first before i bug a buddy to swap MAFs

 

Try resetting the Ecu...via unplugging the battery should solve it

 

I dont really think that would fix it though, It would make the light go away but if it fails twice again it will just come back on..