I heard that some people having problems with the boost they calibrate the radio with the gas end point at around 95 96% and after they give up at 100%
Otherwise go up at 103 104% with your current setup and ceck how it works.
Second: do you have tryed with a different motor if you are having the same problems? A friend of mine with a V3 had a similar problem and was an issue about the sensors (broken)
Hoping this can help you.