If the MAP sensor wasn't plugged in, the motor probably would run, and go through heaps of fuel. The workshop could be correct, as the washdown causes lots of damage to the motor, the fuel doesn't only go out the exhaust, ,it washed the oil off the bores, and breaks down the oil, which wears the crank journals, so to rebuild it to standard would require boring and crank grind, possibly oil pump/cam journal damage. Just because it doesn't make 260rwkw doesnt mean that it wont wear the motor. A second hand rb20 will definately be your cheapest option, and they can be found cheaply in australia on the forum, but till then keep driving it as its unlikely to blow up.