I assume you have a TPI intake? You can test it the same way as a CTS (since it's actually a CTS in there that's measuring the heatsoaked manifold instead - Chevy does not believe in measuring the real AIR temperature with its Intake Air Temp sensor
You can pull the sensor out and measure its resistance at several temperature points.
Use this chart for resistance reference: http://www.thirdgen.org/techboard/at...ase-ctsmat.gif
If you measure the sensor cold, let's say outside on a 50-degree day, you should see several kilo-ohms in resistance (around 5).
If you put the sensor in the freezer for half an hour, you should be able to measure around 25 kohm.
Put the sensor in a boiling pot and measure it at least at boiling point (around 180 ohm). You can also measure points in between, using a reference thermometer, it's up to you. Just like in the good old days of school lab work.
That will tell you whether the IAT/CTS is out of range. Sometimes they just stop reading at all.
Let us know what you find.