The mysterious cylinders are the filter and the accumulator.
BTW you can run the pump(s) in reverse while they are on the car.....disconnect the wires at the pump terminals and connect 12v from a separate source in reverse polarity. I tried this on my 560...one pump ran freely backward and forward; the other ran freely backward and very reluctantly forward. The current draw on the second pump is much higher in the reluctant direction, so I suspect it is defective and perhaps a cause of my rough-running problems. I have replacement pumps on the way.