An observation on the stock air box and water... I live in the rainy Northwest, and a few months back my wife drove our CRD to Seattle and back. The drive back (180 miles) was entirely in the rain. My wife drives like a maniac in the city, but on the interstate she leaves a good 5 car lengths open between her and the next vehicle at all times.
When she got home, I cracked open the air box... there was standing water in the bottom of it, and the filter was damp. When I did the V6 air box mod 24 hours later (the parts had come in the mail while she was away), the Jeep still had standing water in the dimples in the plastic at the bottom of the air box. I noticed a similar amount of standing water after a fishing trip back in early summer, 1.5 hours of driving when I was the only car on the road for most of the trip.
I posted photos of my air box mod... you can see the water and dirt at the bottom of the box, and the bugs, twigs, seeds, etc... stuck in my air filter from the stock intake. This was on a filter with less than 3000 miles on it.
http://www.lostjeeps.com/forum/phpBB3/vie ... highlight=
I think the stock CRD air box design was intended to take advantage of the air pressure on the front of the vehicle at highway speeds to dry and force a bit more air into the box. Unfortunately, it also forces whatever else is in the air at the time as well, such as water and snow, into the air box. A very poor design. While the V6 mod may not increase overall airflow, it likely does decrease the rate at which your filter gets gummed up and restricted.