I have also read that you should avoiding using high pressure washer, however, I was not washing the engine, but the frame rails, suspension etc.
But I agree that the general rule is, not to use a high pressure washer.
"Go to an auto parts place and ask for some vacuum caps."
My understanding after having read the FSM is that the Vacuum Bleed valve should let air in during cranking.
"This valve, along with turning the AIR pump "ON" during cranking, helps prevent vacuum buildup within the AIR system, wich could prevent the integral stop valve from opening"
I will look for an original cap, as just any cap might inhibit the function of the Vacuum Bleed Valve.
I may have to get the complete valve, is there anyone on this forum having such a valve / valve cup available?
Or a GM part number would also help.
//sweabe