Have you ever wondered why is it that EFI vehicles work fine during the rain; engine compartment is not sealed. There is water coming in from everywhere. Water from a hose will not reach the velocity of water that is entering the engine bay when you are driving on an expressway at 100+ Km/h during a rain storm.
I wash engines of all of my vehicles, all of them EFI and coil on plug, with a pressure washer that also injects detergent in the water stream on regular basis. I have yet to experience any malfunction because of washing these engines.