Hi guys, over the years I have read some very helpful posts on this site and I would like to contribute. I know the side skirt parts aren't very complicated of an install but I've seen some threads pop up asking how to install them and figured it might help someone.
Anyways, this is going to cover the install on a 2013 sti (not sure which other years would be the same).
First things first. You need to take the stock side skirts off the car. For that you need to get under the car and pop off the little plastic automotive clips (there should be a total of 7. 6 are the big black plastic circular clips and 1 in the front that you need a small phillips head screwdriver to twist and remove) that line the bottom of the side skirts.
(here is a shot of the fat black plastic clips you will need to remove)
Once those are popped off, use my tried and true method "one-two-yank-foo". And the side skirts will pop off. Your car should now look something like this:
(After doing the first side I realized that the front fender vent did NOT need to come off to get the side skirt off. So you can skip removing that panel.
Once you have the skirt off, now would be a good time to clean them...
Once the actual stock skirt is ready you need to ready the new skirt lips...
Yummy STI goodness from Japan :derp
I wonder why I had a hard time reading these instructions...
Take the now clean OEM skirt and put it someplace you can work on it. I used my workbench (novel idea I know). Place the skirt like-so and line up the s206 skirt lip. When you do this it is very important to start at the rear. So align the rear first. Before you get into drilling holes and such, secure the lip with some painters tape.
I didn't get a shot of my aligning it up. But here you can see I started at the rear and slowly worked my way up.
The hole that you will need to drill will be obvious when line up the s206 skirts. Just go down the line 1 by 1 and drill the hole, insert bolt etc. Here you can see how I had taped the lip on.
As you secure each new bolt it will start to take form and you will soon find yourself not needing the blue painters tape.
If you have read this far I bet you are asking yourself, "what type of nuts and bolts is this guy using?". Well consider that question answered. These seem to be high quality, non-rusting nuts and bolts. As you can see when you do the install, you want to insert the bolt into the drilled hole you created. Then on the other side of the skirt, you want to use a washer, and then finish it off with that extended-rubber-nut-thingy (yes, this is a technical term and will be on the test at the end).