I have had this problem for a while now and always thought it was the tires because I would only be able to replicate it with traction off in the snow. With the big storm here in the northeast area, I decided to take my G55 out and have some fun with traction off. When I turn the traction control off and put the car in first gear, when I go WOT the tires obviously spin and as soon as I let off of the throttle it seems like something from the front end makes a loud screeching noise. I thought it was the tires catching the pavement and therefore making the noise but everywhere is covered with snow so that can't be a possibility.Has anybody ever experienced something like this?

Have you checked the supercharger pulley clutch? The bearings on these have been known to go bad and make noises like you describe