My 05 GT3 just passed 2000 miles. At about 1900 miles it seems the engine gained 25+ horsepower. Less friction as the engine broke in, I guess. I broke the engine/trans in carefully..nothing over 5000 rpm.
Clearly the best running Porsche I have ever driven. Chevron gas and Mobil 1 seem to be the winning combination.

 

Now that you have exercised pure restaint, it is time to reward you and your car by setting the rings. Try rolling on your throttle up to red line a couple of times (w/o attacting too much attention of course). This will help set the rings by putting a higher load on them. Also, a mechanic buddy of mine recommends Chevron b/c of the higher detergent content. I does make a diff what you fill your GT3 with. I too noticed once mine was broken-in, ran smoother with less vibration at idle to cruise speed.

Enjoy,

Daryl