Is there a way of testing the pump in situ to make sure it is producing and maintaining pressure? Then if the pump was working correctly I would have thought the next logical step would be to carry out a pressure test just short of where the possibly faulty sensors are located. Many of the Yeti parts are used elsewhere perhaps if need be salvaged parts could be used. And of course I take it the old chestnut of a blocked breather causing a vacuum in the fuel tank has been ruled out. And being a 4x4 with a saddle shaped tank transfer of fuel is taking place efficiently. Sometimes the obvious is ruled out or overlooked.