Pretty much all of the bolt-on catbacks out there use 2.25" pipes. Thermal R&D sells a turbo-specific 3" catback. If you get a 2.25" system now, it'll be too small once you get the turbo. If you get a 3" system now, it'll be way too big until you get the turbo. Neither option is really ideal. Either keep it stock or buy a 2.25" system for now and sell it when you get the turbo.