The IAT (or ACT if you prefer) has to go after the intercooler. The COSY eec-iv uses the sensor for corrections/control for spark timing, fueling, volumetric efficiency correction, boost control, adaptive learning control, cranking fueling and some other stuff I don't know about (but not the idle for some strange reason on the COSY ecu). For the eec-iv to make the correct decisions the input has to be the temperature of the air entering the cylinders, anything that raises (ie turbo) or lowers (ie intercooler) the temperature of the air has to 'sit' before the sensor in the induction route.