The XFi piston places its single compression ring in a slightly different location than the top ring on the normal piston. I don't know if that's significant or not. The XFi and standard top rings are the same size, but only the XFi has the special "gapless"design. I don't see why you couldn't give the standard pistons the XFi treatment. Maybe the extra/open ring groove will collect goo and keep the other rings cleaner.
Another view of the special gap. Same ring, just flipped for the second pic.
