Hes what I do when I have to run water through the Headers in the drive way. I would first go with what you have said and dont hook up the pump. Second I would hook a Garden hose to your water inlet of your motor with either a lever type shut off valve or a friend at the water spiket and just raise the amount of water pressure up when you put the motor up to 2K rpm. before you lower the idle, lower the water pressure till the headers clear out, then you can lower the idle down. I have down this many times with out problems! But now I have shut off valves right in fornt of the header water inlets, so I adjust it there.