The new GT has electronic torque control tied into the drive-by-wire throttle system, which will cut throttle if it detects that you may lose traction. If it is a consistent problem, bring it back to the dealership- it should be under warranty, yes?
I hate the throttle 'delay off' on mine too- I hear it was one way they got such exemplary epa rating on this little monster, but it definitely gets annoying- first day I had it, noticed its exactly SIX seconds after lifting before full engine braking kicks in- except if its 55-60 degrees then it engine brakes immediately until engine warms slightly- even burbles/backfires a bit if short shifting rpm can actually shoot up a little at pressing the clutch in- 2-2200 rpm seems where mine likes to hang.
Ive read most of the delays can be tuned out, but I'm a little worried about both MPG and warranty- aside from the kinda numb gas pedal feel, everything else about driving it is a blast- well the third gear gate dont allow powershifting very easily, but other than that...My first mech mod desired would be probably the shifter- barking third is just too tough. next on the want list would be a roots type blower for another 100 ft-lb, as this one is lacking a bit of off idle pull, but with the 5 speed, its not a problem...
regarding mpg- I got >24 on two road trips a couple weeks ago- including half-dozen scorched onramps Ive heard 26 is easy to average at 75-80 mph, and dont doubt it a bit...one guy on another forum added a shaker and now says he's getting around 30. next up- true cold air/hoodscoop...
should mention theres a 'adjustment' you can reset:
turn key to run position, dont start.
as soon as lights shut off(few sec) at a moderate speed fully depress accelerator to floor and immediately release at about the same speed
turn off key.
some guys said this really helps a lot, I noticed mines a bit more responsive, but nothing dramatic. theres a thread over at themustangsource.com on this issue.
The shifter is funky and the 2-3 is a common complaint. The remote shifter design is funky- the front of the shifter assembly is mounted to the transmission and the rear is mounted to the body... so when engine/trans are torquing, the front torques with them, but the rear remains stable on the body. The aftermarket shifters ($180 range) fix it by extending the rear mount to also mount on the transmission itself.