I'm happy with the stage I. The shop I bought it from insisted on a free install so I let him. I asked about the stage II and he's run both in his own rig. He didn't notice all that much difference between the two and switched back to the stage I. I keep my EVO in tow and last time I clocked it, 460mi straight highway with a few stops here and there, turned out to be about 16mpg. Summer time its around 19-21. If you want to spend the extra dough, which i think is a few hundred difference, get what you wanna get. If I could do it again, I would make my own. I think there's a tech file, not sure though. Zoodad wouldn't be a bad mod to add, and it involves my favorite word. FREE!!
There's great tech files on that also.