So you punched a hole in the restrictor, creating turbulence, and you're surprised its louder? Punch it out and I bet it gets quieter. Seriosuly. Less turbulence and the muffler is allowed to do what it needs to do, with straight airflow which it is designed for. You just increased velocity through a small free-flowing hole that doesn't allow the muffler to muffle.
If you're looking for a really good silencer rather than a performance muffler, buy the biggest muffler you can fit under the car. You know - one of those oval behemoths that the local Midas stocks.