its because your van is up side down , the epic pump was made for the european market and will not work right in the antipodes position
and we have heard all about you australian pump fondler's
i cant see it being a case of running on oil as it would race away to death from any rev range , whats the oil strainer in the rocker cover like is it possible its pulling through there at high revs with the crank case fumes ?!!is the air filter ok ? it could be so blocked as to make the turbo pull its air from crank case i suppose and pull oil in at high revs
i have similar problems turning off by key sometimes but think its dirt making the shut off valve stick ( 100 ps turbo but with bosch pump fitted ) as a quick clean down of solenoid puts it back to rights for months afterwards