turbo hybrid

Hi, I recently installed a turbo hybrid on my golf 5 2.0 tdi bkd, shaft and impellers of the gt1749vc(ppd170cv). I remapped the whole thing, using an afr of 17 and turbo pressure to 1.7 bar. In diagnosis, the pressure rises a little in an overboost 1.67 and 1.5 is a constant. I have to fix the n75? Should not the ecu modulates the n75 in auto to reach the pressure target? Could be a problem with the turbo? Oh, and under load you hear a noise of suction, but I have to say that all of the tubes have no leaks. The seller says that the noise is normal