I wouldn't be driving on the stock map. The PowerFC doesn't have any of the knock protection that the stock ECU has so if you experience detonation under load (quite likely with the stock PowerFC map) you wont have anything to fall back on except letting off the accelerator. By which time it may be too late and you may have damaged your engine.
The FC's stock map works fine for some and very poorly for others (it pinged a lot on my old R33). In my opinion it is best to drive the car to a reputable tuner with the stock ECU installed, install the PowerFC, and tune. Better safe than sorry.
Unless you know the ins and outs of the FC configuration and your car and are competent at street tuning then I guess go for it.