I got back my steering box re-built from SLS. We have put it back in the car a couple of weeks ago - no issues there, but I could not try it until I got my FIP back in the car.
With steering box in the car, we flushed the PS fluid, filled it with MB 236.3 fluid, raised the front, let it idle for 20min - works great! Smooth movement, no noise, no air, wheels are turning from left to right and back, no leaks - done.