well my mate put the car on the dyno at his work on friday and we had a little mess around with bits and pieces.
turns out that mine was the worst case of rb25 ecu shitting itself that hes ever seen ahaha. the timing was up at 20 to start off with, we took it back to 15 (standard), did a whole bunch of runs on different boost settings and that doesn't seem to make a difference whatsoever.
it seems that every time the car makes boost, regardless of what psi, the ecu retards the timing which makes the boost spike up to 15psi in the mid range, then drop down to set pressure up top where the fueling continues as normal.
we played around with the afm a bit, and didn't really get anywhere. next step for me is to borrow a few things, swap em over and see if it makes a difference.
my afr's were also quite lean throughout the range... still in the safe margin but i might have to look in to upgrading my fuel system soon.
I need to get my hands on:
s1 rb25 manual ecu
s1 rb25 afm
rb25 knock sensor (just in case its not working properly coz that would cause ecu problems)
hopefully the problem is there somewhere. I know that swapping these things isnt going to completely cure the problem, but its better then trying to drive it as it is... power delivery is all over the place