My 8.1L Suburban's stock muffler was notorious for choking power in the name of silent operation. It was a dual 2.5" inlet/dual 2.5" outlet design, but supposedly the inner passages neck down to 1.75" or smaller, choking flow.
I asked Rick (owner of Rick's Muffler in Orem) about a suitable upgrade. He mentioned that due to the Suburban's enclosed body, most performance mufflers would cause lots of drone. However, Flowmaster had made a muffler specifically for a big block Suburban which would increase flow but prevent interior drone. I'm generally not a Flowmaster guy, but since it was made for my exact application I thought I'd give it a try. Long story short: it works. I do get a bit more rumble outside the vehicle, but if the windows are up the difference inside is slight. And best of all, no complaints about drone even on a 1600-mile road trip with my wife riding shotgun and my mother riding in the back seat.
I think Flowmaster calls it the (Super?) 50 Series, maybe? I'd need to call Rick to confirm.
