If the car suffers from lack of power through any rpm in any gear MAF is usual culprit.
You need to come and see me and I can plug my consult unit into your DLC socket, we need to physically see what your car is actually doing.
In my opinion if its holding back are you using a standard boost control valve? Tell me what boost control method you are currently using.
I have 10 years Nissan experience
PM me and ill give you my details. I wont charge for a consult 2 session

While your on here mate.
It will be summat and nothing.
Dont forget Nissan ER (Engine Room harnesses) have a few earths that may need cleaning up. Also check the ecm hasnt got damp.