2003 CTS Manual Trans., '93 STS
Yup, it's riveted. You'll need to drill them out and you'll have ugly holes to fill. I've seen some plastic plugs on the V forum, but I think they're almost as ugly as having holes. There's nothing like a smooth bumper, if your state allows it. A body shop may be able to plastic weld the holes shut and repaint your bumper. It would run a few hundred bucks, though.