Mine never had any lag lucky me but a CAI and tune will cure your problem and put you'll love the extra power.

 

I had a lag in response on my 08 GT. I did a search on here and found a procedure you can do to recalibrate the gas pedal. I dont remember exactly how to do it.....I think you turn the ignition to run ( do not start the engine) then slowly depress the gas pedal to the floor then slowly let up on the gas pedal. It fixed mine!
A tune is not needed.