In two weeks, in Daytona Beach, Florida, 40 cars will compete for the most coveted prize in NASCAR.  As the cars slowly circle the track in the pace laps before the green flag drops, the noise of engines revving will give notice to all of the speed to come.  In a similar fashion, while the U.S. economy has slowed to a crawl over the winter, there are growing reasons to expect a sharp acceleration in the months ahead.