From experience, don't dump it, you'll just bog down. In my STi I rev to about 4,000 and let fairly quickly, but not dumping it. Launching AWD will eat your clutch unless your making enough power to break traction on all four contact patches. In a FWD/RWD drivetrain, the tires are the weakest link in the drivetrain, so they spin. In AWD cars, since there is so much traction, the clutch becomes the weakest link.