Well as we have all seen with fart cans, people do stupid stuff just to be loud. Any of our Cobalts are not pushing enough exhaust gasses to get any advantage from an open downpipe, and it would most likely hurt performance. In response to the original question, open DP setups go from header to dp to cat and then nothing. There are positives to this, but mostly for bigger engine cars, and even then they mostly use cutouts.
My turbo lag is your courtesy head start.