yeah Terry, mine takes a very hefty boot to kick over as well. It has 1075 MTC pistons (I am not sure what comp. ratio, guessing around 11 to 1) and Andrews 2x cams, a ported cylinder head, and vm29 Smooth bores. I have not gone full stupid on it yet, as the chain, sprockets, and tires are god only knows how old, and sketchy...but a 3/4 throttle blast through the gears felt like it might give my 82 gs1100 a challenge on the drag strip.
That is interesting about the z versus kz nomenclature. I may have heard that story, and other explanations before. But I don't remember. Anyway, it seems the Japanese often handle the American market "differently" than the rest of the world. They sure don't send their best products here anymore. Maybe that might change with the introduction of the Euro 5 emissions and mileage standards.