stock is 2.5"? if so you do not want to go any bigger then that for duals. Also if your looking at doing it yourself, get an adapter, its a real pain in the ass if you dont have one. I know from experience. If your goind to take it to a shop and get the exhaust done. Talk with the sales guy once your cars up off the ground and tell him you want to eliminate the Y to a || it will be easier for them and youll get some nice sounds groaning from the car.
As far as CAI I would recommend a demolet intake, or you could make your own custom one, fairly easy.
As far as CAI I would recommend a demolet intake, or you could make your own custom one, fairly easy.