How can one test if the IAT sensor is working?

I've got a FRST OFAC engine which is struggling to return 25mpg (as in its not returned that yet), and I'm thinking IAT could be a culprit. A local tuner said the poor fuel economy could be it running lean at -ve vacuum and turned the fuel pressure up and said to test it at that. It has improved the missfire under -ve boost but no effect the the fuel economy. The car also has a piper t285t2 and is only set up on a 165chip @ 11.5psi on a t2, could this cam cause such poor economy? I know i'm loosing some lower down torque and 'drivability' not running it at high boost and with the foot down all the time, but can it be that bad?

When I unplug it at idle the car does nothing, can I safely drive with it unplugged and look for changed? what changes should there be?

Does a broken IAT return a fault code? does anyone know the code?

Cheers
JAmes.