[lack of replies can usually be attributed to question content]
RA or RB wouldnt matter - any ecu that has been remapped has been done so for the setup of the car at the time - so you could get lucky and it may be slightly better, but it may be heaps worse - all depends on what mods it was set up for...
(ie. if the car it came off had bigger injectors and a z32 afm and you have the stock items it will most likely not run very well)
as for stock RA vs stock RB - the only difference is in the fuel/timing maps (the rally ones are more aggressive)