You should put it on the Dyno again but run it in 4th Gear instead of 3rd.
If it was my car i would be putting it on E85 and throwing a heap more timing at it, that should sort it out
For a basic set up like your doing there is no need to spend much cash on boost control
get one of these.....
http://www.skylinesaustralia.com/forums/topic/73375-i-found-a-good-cheap-boost-controller-for-22/page__hl__loose
yeah Hubs tend to read very high. for example my car has made 411kw on that same dyno with the same turbo as you. 320-330kw would be more realistic for your set-up.
stock 25NEO
3076 .82 rear .6 front cover
E85
1000cc injectors
044 intank
running 27psi
Power FC
Blits Return flow cooler.
As paulr33 said. the exhaust will be a restriction before the cooler pipes will be..
I remember reading some where that it has been done before and worked...
but as nismoid said traction control is useless when you start making a decent amount of power
leave it out imo...