The reduction of both the Spoon b-pipe and N1 Muffler back down to a 2.25" flange (ostensibly to maintain compatibility with OEM exhaust parts) always bugged me. So I got the 2.25" piping and flanges cut out and replaced with 60mm bits, giving the same diameter all the way through.
Along with freeing up the exhaust flow a bit, it also changed the tone (and seemingly the volume) of the noise into something much nicer. Definitely worth considering.