Not familiar with your ride, but found some info online that may help you find the IAC.
""Find you air filter box, follow the black tube that comes out of it. where the black tube meets the engine is the throttle body. Look at the top and back of the throttle body, you will see black thing that is attached to the throttle body there are 2 star head screws holding this to the throttle body and a plug on the top of it. That'* the IAC valve""
I looked and could not find a IAC for your car anywhere, but I could find what is sold as the IAC Electrical connector...
2006 Pontiac Grand Prix GT with SC
1996 Buick Park Ave NA