I also use the louvers in my stainless pipes, had it with the fiberglass/packing.
I pointed them to the back and I don't think their too loud & really like the sound. Here's a link to hear them. (with a big block) Keep in mind, I made the video for the buyer of my engine.
For buyer of my engine #7 - YouTube
At idle-
For buyer of my engine #3 - YouTube