after growing impatient waiting for an rsr gt2, i have made a recipe to build something similar to a cross between the setup pictured in this thread and the rsr gt2. although i know it will be original and sound amazing, i'll share it with everyone.
2.5" mandrel bent piping to a 16" cherry bomb resonator, more 2.5" mandrel piping, 2.5" in/out straight through muffler mounted near rear bumper, then another 1.5' or so of mandrel 2.5" piping exiting the back similar to the gt2 rsr.
cherry bomb resonators can be picked up at most pepboys/kragen/etc.
the sexy but simple muffler i am using is found at summitracing.com