Loosing all electrical power will cause the E.C.U. to reset to basic settings. It will slowly "learn" the settings as you drive it, did it myself when changing to Shell Optimax. Should be O.K. after a cruise around town.
I had NGK PFR6A's in my old R33, worked pretty well getting chased by Audi tt's. Wil be fitting some Iridium plugs in the replacement to see how they shape up, been told they are good for 50,000 mls, will let you know in a couple of years time....