Originally Posted by semtex

I can't speak for Cobb, but I can tell you that when you reflash the new ROM into your ECU with UpRev, that base map is exactly that. It's a base map that has all of the factory parameters, and assumes no mods. By itself, it is not intended to yield any gains. Its sole purpose is to provide the tuner with a platform on which he can load maps that he builds via the process of running your car on the dyno. You see, the factory ROM that comes from Nissan allows no such thing. There are no 'slots' to drop the maps you build into, so to speak. So you replace the factory ROM with UpRev's ROM, and their ROM has these 'slots' for you to plug your performance map(s) into (as well as your valet and anti-theft maps).