for the gxp exhaust it really depends on what u want, do u whant crazy loud or just i nice rumble ? its all completely on preference. i run a 3'' exhaust all the way untill the ypip then its 2.5 but i have thrush turbo mufflers, for days i go cruzing, ihave a cutout b4 the y pip and i pull that off, sounds like a 5.0 mustang, and for show days i have a cutout on the down pipe i open for crazy loud exhaust. for an example of the crazy loud check out my youtube account " joshv1452 " fyi my 3'' exhaust was just made at a shop. i will post a video soon of the sound with cutouts closed
