Hi Julien
So you are using the T3 0.63 housing and you get 1.5 bar at 3200 rpm? that seems fantastic!
Yes, in forth gear ; in 2nd and 3rd I think it's more 3500rpm (with SP 98 fuel). Wastegate pressure is set at 1.0 bar, this may help for spool (and boost is controlled by the original solenoid).
To give you an idea this is against a stage 2 335i (390hp on dyno)
https://www.youtube.com/watch?v=Ocl_F_IcgNYI was really impressed with the instant spool and the power it has even with the small 2.25" flange and exhaust.