What 2005 Mustang GT upgrades should i get?
Since this car is OBD-II compliant you'll be getting a hand held tuner, not a "chip" . The stock exhaust system doesn't become a liability until you are up around 400 HP in the S197 cars. It's pretty nice for a stock system, people who change out the mufflers (axle back) do it for sound, there's not much in the way of performance gains. However these cars do respond very well to CAI's provided you get a tune for them. The stock tune is pretty conservative, an aftermarket tune with a CAI can make noticeable gains and really make the drive by wire throttle more responsive.