I've got the k&n on my ap1 s2k and I'm very happy with it. It's nice and loud, don't have to worry about hydrolock, inexpensive, and I dynoed a 12hp gain to the wheels with the k&n and an invidia test pipe over stock.

 

If it rains alot go with the k&n fipk. the aem filter comes out low, and behind the bumper on the passenger side.

 

I did the umbrella mod and try like hell to avoid deep puddles. I have driven home in some complete downpours. I mean some of the worst rain I have ever seen and had no problems. Now, the car is not my dd. If it was, I probably would go with the comptech or the K&N. But the sound this thing makes is other-worldly....

 

AEM V2 FTMW!

 

i just had the F5 into my bay! Love the growl at just 4000rpm. sounds like i had my exhaust changed! Gain? well.. only 2.5hp on the wheel.

Oh i actually wanted the AEM V2 but couldn't find a model for AP2. So thrashed the idea and go for F5!

Back to F5 or CAI, it will be good on the high end. Power will come at the high side say if you hit above 8500. That's why it is call CAI, not HAI.

 

I have the K&N and love it but it is not the FIPK. I have the one that runs down to the passanger side fake vent, just like the AEM, Fujita, etc. My K&N came with a water repelent boot. I recently cut out the fake vent and put a grill on it and drove the car in the rain. I inspected the filer when I got home and it seems like the boot works. K&N says to replace the boot once a year or more depending on your driving conditions.

K&N claims 7HP for my CAI and 9HP for the FIPK. I think the dyno they have was on AP2 but I am not 100%. All I know is I like the feel and sound. A test pipe or high flow CAT will go nice with your CAI (it did mine).

As for what CAI to go with, I'd say the FIPK for easy maintanance and proven power. I love my CAI but I am very carfull in the rain, even with the water boot (I don't let anyone drive my car). Price was also a big factor when I bought my CAI, I found the K&N for $150 new. The others were all over $200. I think you will be happy with any of the CAIs you listed, just get that nasty heavy OEM airbox out of your car. You will enjoy the extra space you gain under the hood. I can change my oil from the hood now, no need to even jack up the car, just get a flat oil bin.

P.S.
That AEM II CAI install above looks real nice and the lower part of the AEM II pipe looks bigger then mine.

 

 

This one i have to super-impose 2 different pics with diff exposure to show the filter behind the air duct.

 

aem v2! then get a berk test pipe with a fujitsubo exhaust...sounds awesome. haha. just don't drive in any large puddles. if you don't want to have to worry about that at all then maybe the other intake is better.

 

Coming up on 2 years with the AEM V2 I've yet to have any water-related issues and I've been through some SERIOUS rainstorms, to the point of a couple inches of water accumulated on the ground.

I love my V2 but can understand why on a general level people are more comfortable with the K&N. I certainly don't have enough confidence to recommend the AEM if you have any doubts or concerns. Just go with the K&N, it's not bad

Side Note:

Funny thing to me is that countless people are driving around on bald tires, asking to get into a potentially serious accident but they still focus their attention on the rare occurrences of hydrolock. Wild unavoidable storms happen very infrequently while the danger of totaling your car due to poor traction should be a daily concern...