I had "true duals" with "Flowmasters" on a '96 Silverado I used to have. It sounded good, except for the "drone" inside the cab @ cruising speeds. I did gain some performance, but don't need the interior noise.
I thinking of replacing the exhaust on my 1995 K2500. At least a cat back system. Anyone replaced their's with something that sounds good but is not too loud. Truthfully I was thinking of a header muffler in place of the stock muffler and just a single 3" out. My 1989 Chevy has a hole in the pipe just before the muffler and it sounds real good, not loud either.
This forum looked lonely with no posts.
BTW, thew 1989 K2500 is for sale see, Craigslist in Allentown PA.