if you dont get hydrolock with the stock air box in stock form, there's really no way it's going to hydrolock with a couple of extra holes in it.
edit- i've been driving around with an injen on my car for 3+ years and have no idication that hydrolock will ever occur, and i've even driven through some pretty deep puddles. so, yeah, unless you plan on forging some rivers in your 3, you'll be more than fine.