Let me stop you here, before you waste your time and money. The IAT senses the incoming air temp (self explanatory). These readings are used to adjust timing advance, fuel mixture, etc. By putting a resistor in, it's supposed to make the computer think that the air is cooler, therefore allowing the timing to advance more, and a richer AF ratio.
Here's some scenarios for various cars:
Cars with knock sensors (SHO, Duratec and FFV Vulcans)- if timing is advanced too much for the engine's current operating condition, the knock sensor will pick it up, and cut back timing. You've just defeated your purpose.
Cars without knock sensors: (Vulcan) - Since there's no knock sensor, the timing is advanced based on the IAT signal. Advance it too much, and detonation will occur.
Running a richer than required fuel mixture will hurt performance, mileage, and cause faster breakdown of the oil, as well as many other things. Fuel mileage will suffer, and honestly, you don't gain diddly.