I have a 2008 coupe i put headers and x-pipe 3in all the way back to a muffler delete i have a k and n on it question will i be robbing my car of back pressure i have it right now for a tune and im wonder what i should expect from it.

 

You will probably notice a little loss of low end power/torque but you will see more top end power due to increased flow. A tune will definitely help with that.