I'm doing this as a compliment to tomasro's DIY. I'm the kind of person that likes several sources of information.

Thanks tomasro for your guide, without it I wouldn't have tried the install!
Guide: Installing Injen CAI for R18 Civic by tomasro
Guide: Installing Injen CAI for R18 Civic - 8th Generation Honda Civic Forum
I've never so much as changed the oil on my car. Here's a DIY for n00bs. That are nervous like me.
Ok, people. As I said this is to work with the other guides, so I’m not going to beat to death everything that was already covered. There was some things missing from the other two sources and that’s what I’m giving you here. I took over 109 pictures and 1 video. The video is a classic, givin’ that it’s spoken in true Redneck voice. Enjoy the full album here:
peliROJO/Injen - Photobucket - Video and Image Hosting
I’m going to use small pics that link to the big ones. I’m only doing this to ease the burden on Dial-up users. I'm working on building a webpage that will shop all large images.
Tools used:
1 phillips screwdriver – normal size
1 flathead screwdrivers – large blade
8mm wrench
10mm wrench
8mm socket driver
10mm socket driver with a 6 inch extension
Shears
Size 5 hex wrench (bumber only)
Flashlight & other lights
2 car jack stands
2 adjustable pliars
Safety glasses when I reconnected the battery (I’ve heard too many stories of it exploding.)
- Removal Instructions -
1) Remove the battery and the entire battery holder (top & bottom).
2) Disconnect the wire harness clip from the mass air sensor
3) Remove the dual 10mm screws that attach the air intake duct to the metal battery tray
4) Disconnect the air intake duct by pulling it away from the filter box. It’s not connected by anything, so just use some force. After pulling out the top portion the bottom portion was already out, go figure.
5) Remove the top of the filter box and the filter.
6) To remove the lower portion of the filter box you need to disconnect from
four points. Two brass screws, one on the front left, and the other on the back right.
The one on the back right was very tricky and I used a combination of tools to remove it.

ALSO, disconnect the back piece by loosening the clamp and disconnecting the breather hose.
And with a twist the entire lower half of the filter box is coming out:
Here’s what it looks like.
7) Now we are going to disconnect the coolant hoses. ***Make sure your car has cooled down, or else hot blue liquid could burn you. Otherwise a minimal amount comes out, a few milliliters. This is well documented on Injen instructions.
It’s time to get the longer of these two hoses, this is your cooler hose and the other is your breather hose:
Disconnect here:
Follow it around and disconnect the other end.
And finish this off by disconnecting the breather hose (on the top and larger diameter):
8) Attach the 15” – 6mm hose to both sides AND use the stock clamps from the old hose:

I reused this picture but the Injen docs are more than sufficient.
9) Now remove the short Air Intake hose from the manifold:
Twist and remove:
10) Remove the front bumper. Some people haven’t needed to do this. They are able to access a single screw easily from the engine bay. I tried and it was impossible. I’ve removed my bumper before and it’s rather easy. Once you get the hang of it, the bumper comes off in 5 minutes.
The air resonator box is attached with two screws. Remove this box.
Here’s the notorious screw. Accessible from the top? I don’t think so
The yellow wiring harness connects to your Airbag sensor.
Also remove the snorkel and the other tube that’s laying in there, you disconnected from it during Step 4. You will have a pile of parts.

We are getting close!
- Begin the installation –
11) Attach the Injen 2.5” straight hose to your manifold:
Screw it down tight, this is to make an airtight seal. You won’t need to come back to this clamp. But, all the other clamps that you will be tightening do not need to be tightened all the way. There is going to be some repositioning of the pipe and then a final tightening of all clamps. Sometimes it felt like I was bending the pipe by tightening down to much. Keep that in mind, guys. Tight, but we don’t want to re-angle this stuff.
12) Attach the vibra-mount. Washer side UP.
13) Remove the mass air flow sensor from this box:
14) Insert this sensor into the Injen pipe. Notice orientation. Actually, I had inserted mine backwards but the screws didn’t line up. Idiot proof!
15) Connect the pipe to the 2.5” connector:
Position on the vibra-mount. Again, the clamps & mounts do not have to be tightened all that much, you’re going to have to reposition this stuff later.
Not much space between the Injen pipe and the Radiator pipe, but later after reposition there was about 1/8th of an ich.
16) Install the 6” – 17mm breather hose. Mine was a little too long but I trimmed it. Don’t cut it too short, because after repositioning it might not be long enough.
NOTE: Injen doesn’t mention using clamps on this hose. Tomasro suggests it and so do I. I was able to reuse one of the stock clamps but had to purchase a second one.
17) Connect your mass air flow wiring harness to the sensor in the Injen pipe. Route it underneath to make it look prettier.
I read these pages twenty times each!
18) At this point Injen suggests cutting away part of the wheel well. I didn’t do this.
19) Attach the second vibra-mount above the hole:
20) Take your second Injen pipe and attach the 3” straight hose. I wrapped that end in a towel before pushing it through the hole to keep the sheet metal from scratching it.
21) Push it up and connect to the top pipe.
22) Reposition some more and get everything lined up as best you can. Keep the pipe from touching anything.
This is where the air filter will go and it’s touching the sheet metal. I really don’t care, but in a month I’m going to check on it.
23) Tighten, tighten, tighten:

And don’t forget the vibra-mounts.
24) Attach the air filter:
And I took tons of pictures afterward. Put your car’s bumper back on.
NOTE: Let the car idle for 15 minutes.
And the video
http://youtube.com/watch?v=JNtXuZc4hwA