Yes, you can use a DPDT toggle switch, one side of the switch is used to activate the nitrous and the other for the IAT mod, or a SPDT switch and just wire the IAT circuit.
I actually did this on some Northstar powered Cadies with nitrous before the LS1s were out back in 1996, and naturally started doing it on LS1s. It works really well and combined with tuning you can tailor exactly how much timing to retard. The response time is much quicker than you might think, the reason it takes long to show up on some scanners is that the sampling rate is slow. I now usually wire it with a relay so when the nitrous actually activates (when the solenoids turn on) the retard takes place, that way there is full timing during launch until the nitrous turns on and then retards, doing it this way the 60' won't suffer if the nitrous turns on at a higher RPM than your converter stall.
Just keep in mind that a high quality potentiometer would have to be used. Most purchased at local electronic stores probably won't be up to the task, I would use a mil or industrial spec pot. The wipers get dirty and could change resistance or completely open over time from the set point with vibration and extreme temperature changes. This is why I prefer a fixed resistor and make the changes with the tuning software in the IAT tables.
Ive got it hooked up.. will i notice a differnce when the car is on.
Im going to test the system to see if it pulls the timing. Im turning on my nitrous system at idel to see if the cars timing will get pulled when there is power fed to the relay. Should i notice a differnce??
cool, slowhawk... does the diagram look right to you??? OR could you show me/us youre wiring diagram with a 2 pole relay???
i heard if you have a 1997 or 1998 you can use a 4.5 ohm resistor, unplug the weather pack from the iat sensor connection and put the resistor leads into the pcm side of the connector and wrap it with electrical tape and this gains around 10 hp. Is this tru ???