If you have a code intake, you'll want to cover it, plus any electrical components as a precaution. However, there are better methods for cleaning the engine bay. Also, if you have driving for awhile, stop, and spray the cold water on the hot engine, bad things can result. The best thing to do is spray the engine with a water hose under normal presure, then let the engine get warm to the touch, but not hot. Follow that by using an entire can of degreaser and let it sit on everything for around 15 minutes. Rinse well with water again, and turn the engine on to help dry the excess water. Turn it off, and then spray the entire engine bay with WD-40. I know it sounds crazy, but it works wonders. You can use pledge as an alternative, as some belive WD-40 attracts dust.
I'm moving this to the washing section so you can get other ideas. If you don't believe the WD-40 claim, run a search. there are before and after pictures in that forum.
<span style='color:gray'><span style='font-family:Courier'>1995 e36 3 Series RIP
1999 e46 3 Series BURN IN HELL
2000 MR-S Roadster= Current</span></span>