We have not seen any aftermarket company producing a special pump for the S4, most probably because some people knew that the Austrian company will not go far away in the market. Though some very well known and respective racers like the Canadian Mike Klippenstein mostly known as Klipper managed to produce their own tricky version for their super fast S4s. Klipper has been wrenching a lot those four strokes and he has ended up with some very fast recipes. The photo illustrates his tricky pump that was used on one of his Pro Open race crafts.
