Just make sure you get a printout of your AFR (air fuel ratio) against bhp and torque. Armed with these your custom chip burner will be able to optimise the AFR in the new chip across the rev range.
If you use Steve Wong in the States he will programme another chip for free after you have done your modifications, all you have to do is return the first one to him afterwards. I found him to be the most knowledgable and helpful guy on 3.2's next to our own RB.
As an aside I had an H & S system fitted and it made all the difference, particularly to the sound which is now more in keeping with the car and not, as my son said "a hovercraft!"
Last thing ....If your not already doing so I would run your car on 98 RON Optimax as it can make quite a difference to the figures.
Good luck and post your charts both before and after. Most of us going down this route end up the good side of 250bhp and 215lbs/ft