This is the original text from 2006. If you see something that needs updated, please let me know
Okay, this is the real way you do the Keman intake mod. The original is lost and it seems people aren’t doing it the right way anymore, this will clear up the confusion.
GENERAL INFO
The stock intake was designed with quite in mind, not performance. So, it has two air resonators that slow and quite down the flow of air. The stock intake is a true CAI and draws all of the air through a 1" snorkel that goes into the fender. Doing this modification removes both of the resonators, opens up the air box, and makes the intake louder and deeper in sound.
Getting started
You will need a flat head screwdriver, pliers, and some sockets with rachet. A Dremel with cut-off wheels or a hacks-all will be needed to cut off the end of the air box. You also need some schedule 40 2" PVC, a 4" to 3" plastic drain adapter, and a 2" to 2" PVC coupling. Also handy would be some two-part plastic epoxy and clear silicone adhesive.
1. Remove the intake by undoing the hose clamp at the throttle body, the squeeze clamp for the valve cover vent at the air box, the squeeze clamp for the brake booster line, unplug the MAF connector and IAT connector (if you have the IAT connector), and remove the bolts that hold the air box down.
http://www.teamzx2.com/attachment.php?attachmentid=17&d=1208488321
2. Remove the entire intake assembly. Separate the end of the air box by removing the lever clamp, this is where the air filter goes. Remove the air filter and set it aside.
3. Now remove the lower resonator. It sits under the spot the air box bolts to. It looks like this.
http://www.teamzx2.com/attachment.php?attachmentid=18&d=1208488321
It bolts into place and will take a few twist and turns to get it out. You can throw this away. Notice at the bottom of the air box there was a snorkel that went into the resonator. It doesn’t draw air in this way, it just uses that hole for resonating the air.
4. Now, when you removed the air box you had to pull the snorkel out of the fender. There is a plastic-rubber peace that bolts to the fender here. You can remove this to.
5. Now you can cut the air box. Cut it after the ‘R’ in ‘FILTER’ so that you now have a 4-6" opening. Here is a before and after picture.
http://www.teamzx2.com/attachment.php?attachmentid=19&d=1208488321
6. With this opening you can leave it this way or put a sewer adapter in place of the hole, use some clear silicone to seal it up, and extend it to the fender so that you now draw cold air from the fender.
http://www.teamzx2.com/attachment.php?attachmentid=15&d=1208488321
http://www.teamzx2.com/attachment.php?attachmentid=16&d=1208488321
This picture shows the adapter installed but not sealed, you need to put the box back in the car to see how far you have to pull the adapter out to get to the fender before you seal it up with silicone.
7. Now we move to the upper resonator. Remove it and pick up some 2" schedule 40 PVC and a 2" to 2" PVC coupler. Since one of the resonator is bigger then the other, the coupler will make one end bigger. Just put the coupler on the end of the pipe and use the resonator to mark where you need to cut for the right length. To make sure everything will line up, install the upper pipe but leave the hose clamps loose. Now with the intake installed you can adjust it and tighten the hose clamps down. The hose clamps are usually enough to make this intake work fine. But, I’ve found that it sometimes will slide out of that upper pipe and this will make the car die. I used two-part plastic epoxy to seal it up good. It never comes apart now, it will look like this when you are done.
http://www.teamzx2.com/attachment.php?attachmentid=14&d=1208488321
http://www.teamzx2.com/attachment.php?attachmentid=20&d=1208488321
You can paint it to match the intake if you like. Just wait units the epoxy is dry.
8. Now you are done. You have a CAI, if you used the adapter, or a good flowing WAI for much less then buying an aftermarket intake. You can also install a high-flow air filter for more flow through your intake.
-Brad (ZX2Fast)