[RarlyL8]

Blown engines of any type (supercharged or turbocharged) force air through the engine. The more free flowing the exhaust the better.
Low gain or low boost systems will perform better with a tuned exhaust, high power systems perform better with no exhaust at all.
Large bore short pipe headers and a large bore muffler are a must if you wish to optimize the power output. Any restriction in the system will increase heat output while reducing power.

This is a generalization. Many, many other internal engine issues play a part. You should probably consult the manufacturer of your kit for specific information.