Never had one apart but from what I've read the rounded chrome mufflers can't have a cat inside because there's no way to plate them without destroying the cat.
When I cut mine off (I only did it because it's at the end of a tuned pipe, would no longer function properly clear at the end of the exhaust and probably plug up with soot) it looked like looking at the end of a rolled up piece of cardboard and had almost zero restriction.
maybe yours is different then mine. I just got the newer grubee slanthead kit. It can with a black header and muffler. Inside there looks to be a whole mess of stuff. The guy I bought it from says its a catalytic converter.
It looks rather restrictive, but I can see the other side of it without cutting the muffler at the welded seam