well, it was promised so here you go :-)
what you see in this picture:
the dark red line shows torque with the stock Z34 manifold setup
the blue line shows torque with the GTR manifold setup
first thing you notice is that the torque starts higher right from the beginning, in fact it is at about 320NM (236ft.lb) vs. 250NM (184ft.lb) at 2200RPM.
Until 4200RPM it stays about the same with both setups but then you see an increase up to 20NM (15ft.lb) until 5200RPM and an even more noticable increase of nearly 40NM (29ft.lb) from 5500RPM till 6500RPM.
My first guess is that the dent around 5300RPM comes from the ECU (which has no tuning currently). It might be that there is some sort of torque goal /limit and the ECU notices that torque exceeds this maximum allowed value so it is reduced, then goes up again, and is reduced again.
Maybe someone here who has more experience with how the ECU works can shed some light in this issue - does it make any sense ?
As power is calculcated in relation to torque you of course see the same increase and "issue" with the light red vs. the red line for HP.
Overall I'm currently very satisfied with the results. My street driving experience and feel obviously were not too wrong, the car really has more torque in certain areas and is at least not any slower or weaker than with the stock setup.
Next step is tuning the ECU for the new setup - I'm very positive we can eliminate the dent at 5500RPM and maintain a higher torque and HP across the whole RPM band.
Stay tuned for more results soon - for today I'm very happy and thank you again for all your support and positive feedback !
Chris