Why is my (97) galant stalling?

When I come to stop light my car tends to drop Idle and stall, this is after its warmed up. I had it plugged in and it reads a Idle System Malfunction code, so i replaced the throttle body, TPS, and AIC sensor. I also replaced the battery, plugs and wires, and valve cover gasket set. I cannot figure this out so i bought a new ECU but before i go abouts all that work, Just wondering if their is any other little things it might me?