There is at least one good Stealth CAI guide out there right now. You can find it HERE
. I used it as a basis for doing my own stealth mod. Other than that, I can't find a proper guide or even guidance from others here regarding the pro's and cons of this method of introducing a Stealth CAI to your Focus. I'm not providing pictures because while I was working on the car, a freak storm occurred and brought two tornadoes with it. In other words, I was doing a lot of ducking and covering thanks to the healthy wind, rain and hail. The second tornado got so close that things were being sucked out of the yard and the covered garage area I was working in. Sounded like a freight train going by! I digress.
The tutorial does a good job of using pictures to show you what to expect. In all fairness though, the tutorial does a poor job of describing what to do when you're prepping the car for the mod. I believe the author's intent was to focus (no pun intended) on the actual mod itself rather than what comes before it. This is my attempt to help you out in some small way so that you'll not only know what to expect, but you'll be better prepared than I was and it could save you some precious time if you're trying to get it done and get on with life.
I know that not everyone has a nice hydraulic floor jack, but I'm blessed with a father-in-law who has just about everything you'd possibly need to build or tear apart a car. In the worst case scenario, you could use the jack from your trunk to lift the front driver side wheel high enough to remove it. Take caution when doing this as those jacks aren't especially steady. Make sure you're on solid, flat ground. I recommend a driveway or parking lot. Also make sure (for safety's sake) that you put a block under there to assist in keeping the car stable. The last precaution is using your E-Brake. This helps keep the car stationary.
Once you have the car jacked up and the wheel removed, the fun part begins. The tutorial states that you should not only remove the wheel well but also the splash guard on the front of the car. Removing the splash guard is not only a waste of time, but a PITA. The wheel well removal is fairly simple if you know what you're going to be doing. There are about 5 Phillips screws and one small bolt (sorry, can't remember the size right now) that you'll have to remove in order to see and remove the factory air filter. Keep in mind that the Phillips screws are secured in a fashion that's similar to drywall mounting screws. There is a quartered piece of plastic that surrounds the screw. Once you loosen it enough, you can pop it out of the body with no problem at all. The key is to keep loosening a few turns more when you think you've done enough. The cover is sitting in two small slots to help secure it in place. One of them is at the top of the wheel well and the other is near the driver side door. They easily pop out and you can push it around to remove it out of the two slots it's sitting on.
Once the wheel well is free and clear, you can remove the two bolts that attach the factory air filter box to the frame. Once those two bolts are out, you can easily follow the other directions and have a great deal of success.
NOW: Here's what else I learned the hard way. The author states that a filter with a 3" ID will work but it's a tight fit. I'm here to tell you now that even attempting this is a waste of 25 dollars in a filter. I kept at it for an hour and still couldn't get it on there properly. Even my 6 year old started repeating my mantra of "Almost...Almost!" every few seconds. After he finally said: "Daddy, that filter is PWN'ing you!" I got the hint and went back to the store. My solution was an APC filter from Advance Auto to replace it. The filter had three ID choices in 3, 3 1/2 & 4 inches. AGAIN! Don't bother trying to use the 3" adapter. Simply use the 3 1/2 adapter. At first it'll remind you of the old adage: "Like Parking Your Bicycle In An Airplane Hanger". Take heart. The filter is equipped with a hose clamp that will not only correct this issue, but do a darned fine job of it in the process. Once that's done, follow the rest of the instructions to put it all back together. Keep in mind that the two bolts you removed to take out the stock air box will no longer be used.
When you first crank up the car, be prepared for a bit of sputtering and maybe a mild backfire when you rev the engine a bit. Your ECU is going to have to adjust to the change you just made. Let it idle about 5 minutes and you're good to go. The throttle response is much improved and you'll feel the extra torque. This is by far the cheapest mod you can perform on your Focus and actually feel the difference it makes.
Enjoy and feel free to PM me with any questions you may have!