well it does add some power. I noticed a change in performance when i put mine on. As far as the overheating my car has not overheated and i have been on it autocross racing and it has not overheated. I have noticed that when I have my headlights on with my fog lights, my gauge lights, and my radio that the lights dim. But for the average person that is not really going to happen. I mean with just my headlights on and the radio at a normal level the headlights do not dim. It does reduce the output of your alternator so if you have a big stero system it will cause your battery to go dead and not get charged because you will be maxing out your alternator.