Without going into a lengthy explanation of the EFI ignition system, the short version is that your cars sensors will be continually trying to warm up the car. You will get a rich mixter below about 170. Poor fuel milage and various problems with your tune will surface.
That said, the HOTTER you run the motor the more efficient it will be. That means it will make more HORSEPOWER! It is the intake charge that needs cold air.