Helmwurst

Recently came across Service Bulletin 2001-03. This explains that the Service Manual #6 shows the thermostat installed incorrectly in the HP500 EFI. It also states the thermostats were installed correctly from the factory. This SB shows the installation to be from the top down, cover, gasket, thermostat, gasket, spacer. #6 Manual & #3 Manual shows, cover, gasket, spacer, gasket, thermostat. Can anyone explain the reason they made the change on the EFI and not the carbureted models ? When I went to change them out on a carb model, they were like the SB shows and not the manual. Why the change and what is the difference in water flow? Is there another Service Bulletin that shows the carb models should be installed the same as the EFI or the way they are in the Service Manuals. That's a long time of running them one way verses the other.