Thanks for the explanation, tsuwm, about sandbagging.

In my usual ignorance about all things related to all sports, I had thought maybe sandbagging meant (get ready to roll your eyes) that the car in question appeared to be running slowly because sandbags had been attached to it. Then voila! Suddenly the car speeds ahead and you realize the driver was sandbagging--driving as though weighted down with sandbags.

Very nice to know the truth of the situation now.