I have found that the smaller the pipe and/or less crossover the more crackles and more drone. 1 of my trucks has shortys 3" collectors that has been y-piped into a single 4" into a modified flowmaster 40 that's single 4 in dual 4 out(used to be 3in dual 2.5out which was a little too crackly/droney for my liking) it sounds awesome really rumbly and little to no drone just loud, I have capped 1 outlet before and that made it a lot quieter. Another truck I have has headers dual 3" x-pipe into a dual in and out 3" magnaflow straight through muffler which then exited behind the cab, that was really droney especially between 1700-2200rpm and ended up y-piping after the muffler to a single 4 into a mbrp straight through, 4" over the axle and out and that really made it a nice daily driver, cruised 65mph at 68-71dbz inside the cab (the dual 3 out the side was 80-85dbz). This guy I know runs dual 2.25, h-piped flowmaster at one point and borla mufflers with manifolds without cats which crackles at an idle, really obnoxious, drones the hell out of the cab, not my cup of tea but he likes it so to each their own.