My eyes are starting to bleed from seeing so many different variations of this question.
I wouldn't personally replace the axle-black exhaust with a cat-back, the stock tube's flow fine -- i.e. it would be a lot of money for like a 2 horsepower gain if that.
I would recommend a tune forsure, followed by long tube headers, followed by a boss intake or cobra intake with a matching CAI.
The 2011 GT doesn't respond to CAI and Cat-back like my 03 GT would have. The stock CAI and tubes flow pretty well already.
For more details, don't hesitate to search the forums. I myself asked a similiar question a while back trying to get my 5.0 to 500 at the crank with bolt ons.
I wouldn't personally replace the axle-black exhaust with a cat-back, the stock tube's flow fine -- i.e. it would be a lot of money for like a 2 horsepower gain if that.
I would recommend a tune forsure, followed by long tube headers, followed by a boss intake or cobra intake with a matching CAI.
The 2011 GT doesn't respond to CAI and Cat-back like my 03 GT would have. The stock CAI and tubes flow pretty well already.
For more details, don't hesitate to search the forums. I myself asked a similiar question a while back trying to get my 5.0 to 500 at the crank with bolt ons.