To make a long (and ongoing) story short: the 2013's heat extractor hood drains water on to the fusebox cover on the passenger side, and on the airbox cover on the driver's side.
When you install a CAI, the new filter element is where the airbox lid is, and it gets wet when it rains/you wash it/otherwise get the hood wet. This isn't a point up for debate, the filter will get wet to some extent if water gets in the hood vents.
A few manufacturers have made videos explaining that this isn't really an issue, but the community of '13 owners are adamant that they do not want water from the vents to drain on the intake element. The question of the day is this: is the amount of drainage from the hood vents enough to cause problems, such as hydrolock or otherwise?
There seems to be one manufacturer that seems to think so, and C&L has designed a CAI system that eliminates this problem: here is a link to their website where it shows how they took the shroud and added a plastic sheet to channel the water away C&L Air Intake System for the 2013 Mustang GT
This leads me to believe that water getting on the filter CAN be an issue, or they probably would have not changed the design from the 11' and 12', after all, it costs $$ to R&D a new product.
What is American Muscle's opinion on this? Is this an issue that needs to be addressed with the line of intakes that are marketed to 13' owners that currently do not have this shroud?
My recommendation is this: sell a shroud similar to the C&L one for use with the other CAI systems. Most CAI systems use a very similar shroud, I honestly think this could be a "one size fits all CAI-equipped 2013 mustangs" thing. Make it somewhat cheap to buy (or...at a discount for the guys who already purchased one while not knowing this was a problem?) and you'll ease a lot of '13 GT owner's minds.
Thanks for your attention into this matter!