Never had a problem on my M50. However, I think the plugs are covered up a bit more on the M50. I also cover the fuse boxes and elec components with foil. I srpay a warm engine with gunk or similar. Let set for 15 minutes and rinse off with garden hose. start it up, rev it a couple of times to shake off water. Thats it.
Thanks,
1995 525i Auto, M50TU 2.5L, EAT chip, 1/95 build, USA, 205/65/15 tires, ASC+T, HID, lumbar, EC Mirror, BMW Alpine 5 radio with BMW-Pioneer CD Changer, abt 236k miles, Oxford Green/Parchment