+1Unplug and spray WD-40 in the crank sensor, cam sensor and coil pack plugs. It will drive out any water. Also check each end of all spark plug wires. Those are the major areas that come to mind. Hth
I used to pressure wash mine all the time and never had a problem. That being said however almost every time I did have a problem with the way the car was running I traced it to a bad connection.
I'd undo every connection under the hood, spray with Water Displacement #40, then contact cleaner and then make sure all the pins are making good physical contact. After 30 years they get loose and corrode.
Even corrosion you can't see will make a high resistance connection. I bend the pins slightly to get a good physical connection.