On the Nissan Plant Tour in June, I asked if the 2000-2002 Xterra could be tweaked for the extra 10 horses. The Xterra dude(engineer,tech, whatever)told me that if the dealer or anyone else tried to tweak the older Xterras, it wouldn't run the same, he recommended against trying it. I then asked how they got the extra horses, he said they tweaked the ECM, the fuel mixture, the EGR, and some other stuff.