First gear stuttering

See if reinstalling the tune and recalibrating the gas pedal/throttle body helps.

i have been having a simular problem where the car bucks, expecially when its cold or i have been driving on the hwy for a while. it just dies and then blips the throttle for a sec then settles down. its expecially violent when trying to get on on-ramps and such where your getting on it a bit. from what i have read on the forums and tsb's what is causing my issue is more than likely a fuel pump. i have also noticed at night with all the lights on the heater or a/c on and the stereo up the my car surges much much more, even with cruise control on you can feel it. altho that may just be because of the current being pulled from everything on. kinda sounds like you may be having the same issue that i am, seems to be pretty common on these cars

I just got an 07 GT about a week ago, and I've noticed that mine does the same thing. When I've just started it and I try to start out slowly in first, it will buck pretty violently sometimes.

Just like the OP, I can't really pin down a time when it does it. It does in intermittently.

Mine does it also. Seems like only when it's cold. Probably normal.