The IAT mod is using some sort of resister to make the PCM think that the air outside is cooler then what it really is. Doing this makes the car run lean. It's "supposed" to smooth out the rpm band in the upper rpms.
But i have heard it's not good as it can cause detenation.

Read this post. It explains alot better. IAT mod

Simon W. Las Vegas.
96 SE V6 MTX Tereador Red (1st Blown Engine, better be the last!)
1999 SVT Engine
SVT Exhaust w/custom DTM Tips and optimized Y-pipe and no Res (thanks to Po-Jay!). LSD Quaife(thanks to Terry!), SCA CAI w/KKM, Grizzly clutch, FMS 9mm wires, Airknights custom short shifter.

"You can only get more rice at one time by ordering Chinese" - Davo7SVT
"it's only nuts and bolts" - Terry Haines
"Drive it like you stole it" - Me!