The ambient temp sensor plugs into a harness which lives behind the front bumper and then is inserted into the 'o' shaped receiver in the plastic grill on the pass. side. I doubt it has much effect on performance, if any.
This is because there are numerous temp sensors throughout the car including one which is integral to the MAF (Mass Airflow Sensor). If the DME uses it at all, I suspect that it 'weighs' the various sensors assigning differing priorities to each. For fuel mapping, the air charge temp sensor (MAF) and the coolant temp sensor are likely to dominate.
The sensor in the front grill is mostly a convenience sensor for the dash display and also figures into the climate control, although this too has numerous sensors in the ductwork and cabin as well as sensors for solar radiation in the dash which all combine to allow the cc to select the proper temp and fan levels.
