I didn't have an OFFICIAL Pypes cat-back with Violators, just the muffs clamped on in place on what had previously been a Dynomax Super Turbo cat-back (2.5"). I imagine it sounds exactly the same as the production cat-back, anyway ... which is to say, it sounds friggin' AWESOME.
Behind a cat'ed X- or H-pipe, it's not bad, but kinda mellow; behind an off-road X- or H-pipe, it ROCKS. Raspy and kinda hollow like a chambered muffler, but without the obnoxious Flowmaster-style drone, and with the flow characteristics of any other straight-through muffler.
Only downside is that I've heard some folks have had problems with the fitment of the tailpipes, with regards to where the hangers are located, but if you're running dumps or you can live with maybe needing to modify the hanger(s) a bit (or if you're just not anal about how your tailpipes look), then it's a helluva bargain in a cat-back.
I plan on throwing a pair of Violators on my '86 after I convert it to a manual.
EDIT: Again, video clips of Pypes exhaust do NOT do them justice at all.