[signalpuke]

What is the difference. Just wondering.

Perforated is like a Basketball jersey on the inside of the muffler, louvered is like a cheese grater. I will try to find pics, but the perforated will flow better because it is not only less turbulent, but the louvers cut into the air stream.

Here is a louver

Perforated

I will look for more examples, those are small pics.

Here we go!