power cut out

[hefer81]

I need some sort of guide as to why on low boost my dyno curve is nice and steady. On a high boost setting the curve will go up then cut out go down and power returns then starts climbing agin but the high boost setting still only will put out roughly the same if not slightly more power. On high boost it will reach its power level then sort of run on a constant power plain where it feels like there is still no more power left and does this relatively early in the rev range. I had a boost tune and noticed that the fuel cut is around 12-13 psi so we set this just below what do you think will fix this problem. I am aiming for a power fc as this is what i think will fix this problem as it does feel like their is some sort of limit when it hits a certain power level please any suggestions would be good