Grubee GT4 Carb Issues

Hey all,
So i have a Grubee GT4 with an NT carb and i cant seem to get it to run right. I thought it was the main yet, so i bought jets from 64-78 mm and they seem to do nothing for performance. I thought there might be a blocked channel in the carb so i took it apart and cleaned it and nothing changed.
the problem is that it runs well up to 3/4 throttle, but when its fully open it gets to about 25-27 and acts like it is running out of fuel. The result is that my top speed varies between 25-27 with periods of it sounding like its dying then getting more power. I've read a lot of threads and just cant seem to figure it out.
Anyone have any suggestions?