There really never was a "Gen 2" Mini 160, only minor things were changed with the Gen 1 Mini 160, such as relocation of the silencer. The Mini 160 never got the big impeller and pump head upgrade like the Mini 180 and Mini 200 did. For the Gen 3 on all of the Mini's they all now have the AKB (Anti-Calcium Bypass) loop on the pump, just like the larger motorblock Super Marin and Delux skimmer line.