theres 3 things it can be 1 the iac or the wireing and last ecu since you replaced the iac with a known good one then it leaves wireing or ecu , i'm assuming this a 2nd gen b16 with the gray plugs and not the old 1st gen with the milky white plugs as if so the OBD0 dizzy and iac are diffrent then then the OBD1 ones