Has anyone ever had this problem:

I rinsed out my engine compartment and the car started running really badly. I checked to see what was causing it and found water in the spark plug holes. 2 or 3 of them had a LOT of water in them and the others just a little bit. And it wasn't like I used a high pressure hose/nozzle or was forcing water at close range or anything - just a quick rinse. This shouldn't have happened.

There is no gasket on that cover, so water can get in.

You are lucky you did not get water in a sensor, a switch, or some other component. Washing your engine can be quite costly if water gets in the wrong place. If water were good for your engine, why do we have a hood over the engine? The rain would clean up for us.

I hope you did not use a butyl based detergent, in strong concentrations they can drastically shorten the life of rubber components.

I like to clean metal surfaces with a little kerosine and a rag or Q-tip. With a little patience you can clean all the nooks and crannies on top of the head.

For "soft" parts like rubber and plastic, I have had some success with a little WD-40 and a rag or Q-tip.

I try to spend a few minutes with a small rag cleaning every time I'm under the hood to check fluids, which is weekly.

I hate big cleaning productions, I just like to keep ignition parts clean to avoid misfiring, and to keep gross amounts of crud down to a reasonable level.
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2 8s & 2 7s 600,000 miles total

uSED CAR LOTS WASH THEIR ENGINES EVERYDAY AND WE CHARGE THEM 1 HOUR OF LABOR TO DRY THE HOLES OUT AND RESET THE CHECK ENGINE LIGHT. THESE GUYS SHOULD KNOW BETTER AND THEY STILL DO IT.

.....but that'll happen everytime you wash your engine, I see that often and the solution is to not wash the top of your engine unless you are prepared to remove the water from those holes. It's easy if you have a compressor and can just blow the water out.