I just realized there isn't a DIY for this in the E90 forums!
If you have an E90 N55 or N54 this will or has already happened to you around the 60k mile interval. It won't leave you stranded but it sure as hell sucks!
Don't even think about calling your dealership and spending $500 on a new plastic pipe that will pop again. Slap some duct tape on your broken pipe. Drive home and order a VRSF pipe or any metal pipe you can find.