GS does not have the same secondary cat (resonator) config as the coupe or the spyder. x-pipe is standard. I think it will be loud (very loud) when mufflers are replaced with straight pipes....I'm thinking to do the same with the GS, not removing the resonators, just remove the mufflers and cats only and replace with straight pipes. cardiffgiant, is the CEL lights not ON by removing the mufflers and replacing cats & resonators with x pipe? Do u have any videos?