The ECU has programming which within pre-defined data points allows the ECU to adjust the engines performance through injector timing. This is similar to when the car is driven to higher altitudes or the air intake temperature changes as well as the coolant temperature. The ECU thus can also adjust to increased air flow so long as it stays within the data pre-programed and a simple change of a Cold Air Intake is within the ECU ability. However, a tune will give better performance just as when boost is added with supercharger pulley changes it then becomes necessary to reprogram the ECU ( commonly referred to as "tuning" ) to get the best performance.

Edited further: There are tuning shops that will give the Crossfire a "tune" that they have found through experience fits the changes you tell the tuner you have made to the car. Euro Tune is such a shop in that through a computer connection done at your house they will tune your Crossfire to the specs they have found through the years to best match your modifications. These are inexpensive compared to a tune involving a run on a dynamometer which is custom to your specific car.