chevykid168 hit the nail on the head.
Replace your fuel filter. It's probably getting close to the end of its life. Not restrictive enough to slow fuel flow on the stock tune, but on a bigger tune it's not getting enough fuel at full throttle. The studdering before it shifts is BY FAR the most common symptom of needing a fuel filter.
Get it changed and I bet she'll run like a dream!
We've got an awesome deal on wix/napa fuel filters as well. 2 filters shipped to your door for about $60. Let me know if I can help
-Jesse