My "flex" pipe (I call it a down pipe) was broken into 2 pieces that didn't really line up anymore. It was as if I had a 10" Exhaust system length, boy was that loud
When I replaced it I was actually worried that I knocked something related to the turbo loose since it was so quiet and acted differently. Everything was fine it was just the fact that I never heard it with a proper exhaust system on. My friend said he could actually hear me down the street while he was inside while my car was running before I fixed it.