One thing to consider is water and your mass air flow sensor don't mix well, I know a guy with an STI he sucked water in and it sent his maf/tune haywire, almost cost him another engine and it took a day on a dyno to straighten it out.

 

ever since i took mine off the car cools down 3 times faster its ridiculous how much heat that thing traps in the bay, also if you have an aftermarket exhaust mani there could be possibilities of cracking when touching water, but here in socal weve never seen rain

 

Have had mine off over a year and also have an open filter intake. No problems.