Good write up there Andy.
I didn't think 288 was too bad a figure at the wheels, the 313 quoted by Nissan is PS not BHP. The BHP is more like 309, and earlier cars seem to loose similar amounts though the trasmission on the dyno. Furthermore having the Nismo CAI on a stock ECU will not get you any gains, the ECU dials them out.
Looks like a good result if the cost was reasonable.