None. So S&B and perhaps other CAI manufacturers understand their product vs potential water entry and debris. Rather than engineering baffles to address this in general, they sell an optional filter cover at additional expense that requires more frequent maintenance. Hum. The video example showed a paper filter, not the oiled one. Wonder if there is any difference?
Yes I have one on my mustang and it still made 800whp with it. I use it to keep the exposed filter dry going into the blower.
Most sand rails have the cover. You have to. Never had any problems. I would get it