Originally Posted by dezertrunner
Unless you're racing, you don't need a prefilter. I race and I don't even use them sometimes. Also, they might "repel" water to a slight extent, but if air can go through so can water.
Your best bet for filtering is a standard paper type filter. They're is a reason that type of filter has been around forever, they work.
I ran a BHAF (huge paper air filter) on my 97 12v, and I also ran an outerwears prefilter, because the filter itself was subject to getting wet being in the open.
Never had a problem, and the outerwears kept the water out, even when the garden hose was held on it as a test.