The mbc is causing part throttle limp mode. Basically the mbc is allowing the turbo to boost earlier than the n75 valve would have allowed. Under hard acceleration all is good but on part throttle you can hit limp simply because your making more boost than the map requests. (map is set to limp if deviation exceeds 2psi between requested and delivered).
The only way to make more reliable power is as follows.
1. replace 6psi actuator with a Forge unit and uprate to a 10psi spring.
2. Increase the boost requests of the map with lemmingwinks, vtune, sp3 etc.
3.Increase fueling with the above software.
4.Connect your boost controller in parallel with the n75 valve. This will prevent any part throttle limp and allow the mbc to keep the turbo spikes to within 1.6bar.
set mbc to operate @ 1.2 bar.
you should hold 1.3 bar to the red line which will be a huge kick, by keeping the spike in check should reduce strain on the stock turbo.