I own a 2008 Grand Prix V6 3.8 L. When I first take off when the car is cold and make a hard left turn I hear a growling noise coming from the engine. It is louder when I accelerate and lets up when I decelerate. After about 15 miles or so it seems to dissapate. Not sure how to troubleshoot this. I opened the hood and it sounds like the noise is coming from the alternator. Is there a way I can verify this?