We are looking for some more power out of our 8920. We had it at the local implement shop and he dynoed it at 155 hp. After turning the screw it did not change the hp at all. He said the pump would have to be taken off and sent to a pump shop to be turned up. Is this correct? I thought this pump could be turned up like the older magnums. The number on the pump is RSV 500 1100MW0A368. Any help would be appreciated. Thanks.