To use a 4 wire STEPPER style IAC (stock GM TPI/TBI) you need to make a 
small adapter circuit. You will need a small breadboard or PC board, and the
DP_Stepper-K kit from DiyAutoTune. This basically converts the two IAC1 and IAC2
control wires on the Microsquirt into 4 stepper wires required for GM IACs. This
uses a IDN2916 chip to drive the steppers directly. The following is how to wire it:

Microsquirt             UDN2916     Notes

J1,  Pin 7 (PT7) -----> 10          IAC1 COIL "B"
J1,  Pin 9 (PT6) -----> 16          IAC2 COIL "A"
J1,  Pin 10 (enable)--> 17,8,9,20   IAC enable logic
J2,  PIN 15(+5 vref) -> 11,15,13    Power


'165 ECM      DESC    		UDN2916

C5 (BLU/WHT) "A HI" IAC-2A      2
C6 (BLU/BLK) "A LO" IAC-2B      5

C4 (GRN/WHT) "B HI" IAC-1A      1
C3 (GRN/BLK) "B LO" IAC-1B      21
A6 Switched power on            24

Please follow the schematic below to wire the circuit. 


Iac Wiring MOPAR vs GM: