Oh and to get a better idea of the problem - when you romp on it the RPM's go up and she doesn't shift until you back out a bit but under normal acceleration she shifts fine?
I know mine started doing that after I loaded the Predator tune on her - after about a week of running detuned. I was three updates off on my Predator and one of the updates addressed a "shifting problem". I updated it and re-tuned and she's running better than ever. Are you tuned by chance or stock?