https://cnrautoparts.com/exhau....st-uppipe-for-for-6-
Up-pipe is a piping that connects the exhaust manifold with the turbo. Down-pipe is a piping that connects the turbo with the rest of the exhaust pipe. Exhaust gases leave the turbo from the down-pipe. In those cases, the turbo tends to serve as a bit of a muffler; at least I think it tones down the blare as compared to a naturally aspirated motor. Deleting catalytic converters is also not uncommon, but is not something we recommend as it can negatively affect sound and performance. Even though this