Originally Posted by kagraham
This may be way off base, but is my only experience with modifying stock mufflers!
Before I turned 16 I had a Go-ped, a scooter powered by a 25cc 2-stroke weed-eater engine. Of course I began to modify it, and the first thing to go was the "floss" insulation that was in the tin-can muffler (made the scooter louder and supposedly added some sort of performance...who-knows)
Obviously the differences in application might be more than the similarities, but that insulation definately decreased the volume, and raspiness!
I'm really glad you're willing to begin some experiments. My scientific mind says, change one thing at a time so we can determine exactly what needs to be done, no more no less.
I would remove some insulation, leave the existing perforations and see what you get. If indeed that is a cat, I suspect it would be best to make the left and right symetrical.
Makes perfect sense, I never messed with exhaust to be honest with you so I'm going to leave it up to you... I'll just might start with some down pipes... maybe that will make it sound deeper...