To answer skyr34's question, yes we have the Datalogit software for most of the Nissan range which does make the tuning a little easier and quicker.
To give an idea of costing , an initial Power FC tune on a vehicle we see for the first time is $450.
All subsequent tuning is purely dyno time at $140 per hour but with most of the bolton mods you would normally do to a Skyline, the additional tune time would only be 1 or 2 hours max.
Cheers
Ken