I believe the bumper covers on the R129 are made of polypropylene. I would like to strip the paint from these covers since the previous painter did a sh---y job. You can lift the top coat with a razor blade. Any reccommendations for a stripping material?

If you can lift it with a razor blade, chances are you can blow it off with high pressure air. Protect your eyes of course. Any paint that doesn't come off with the air will have to be sanded off. I don't know of any chemical stripper I would use that positively won't screw up the bumper once it eats thru the paint.