Small Flathead screwdriver
Medium Phillips screwdriver
Medium Torx screwdriver
13mm socket and wrench
I used the K&N RB-0900 in my SAAB 9-5. I purchased it from (of all places) Amazon.com and it cost less than $30 with free shipping. Any similar universal air filter with a 3 inch flange should fit. There is plenty of room behind the fender, so the size of the filter element is up to you as long as it has a 3 inch flange.
This took me less than one hour to complete.
The stock air box is located between the passenger side wheel well and the bumper. There is a plastic tube that goes from the side of the air box, across the back of the bumper and up behind the grill. There is a rubber tube on top of the air box that runs inside the fender and through a hole under the hood to the mass airflow sensor (MAF).
These instructions will remove the box and both tubes. The rubber tube is then reinstalled with the new filter attached.
Under the car: Remove the two nuts that attach the air box to the car and loosen the hose clamp on the side of the air box. A photo of this area
Under the car: Remove the screw on the under side edge of the bumper near the wheel well and the two screws that connect the plastic wheel well to the edge of the front bumper. Remove the four 13mm screws and four Phillips screws on the large plastic engine guard panel under the car and set it aside.
Under the hood: Remove the two plastic pressure screws that hold the grill in place and then remove the grill by lifting up and out.
Set the grill aside. Remove the 13mm screw holding the air intake tube to the bumper. The intake tube is already removed in the photo below, but the screw location is marked, along with the other half of the mounting bracket.
Wiggle the hard plastic tube to detach it from the air filter box. Store it someplace because it won't be reinstalled on this modification.
Under the hood: Unscrew and pull out the passenger side corner lamp (I didn't do this and ended up breaking the light clips as I pulled the air box out).
Loosen the hose clamp on the MAF that is closest to the fender and remove the rubber tube from the MAF with the help of the flathead screwdriver.
Under the car: Push the stock air filter box up and over to clear the bracket. Push the front bumper and wheel well to the side and pull the box down. It should come out with a little pressure.
Once out, loosen the hose clamp and remove the rubber tube. Put the box away because it isn't reinstalled in the modification.
The rubber tube and your new universal air filter with 3 inch diameter flange will connect together and the hose clamp is then tighten.
The tube and filter can then be routed back through the fender and reconnected to the MAF. I used silicone adhesive and a small square of stiff foam rubber between the tube and the inside fender wall to keep down wear and rattling.
Reinstall the three fender well screws, the plastic under-engine panel with eight screws, and the grill with plastic pressure screws. Clean up the area and put away your tools.
Start the car and check out your work. Enjoy the test drive. Idle and low speed driving sounded the same on my SAAB, but the turbo can really be heard now when you give it some gas. I can hear the turbo with the windows up, but the most fun is with the windows down.
Some people will have concerns about rain water getting pass the filter and into the engine. You will want to install some sort of splash guard if you are worried. I'm running around without a guard and will report back if I end up having any problems. See update below.
UPDATE: I just drove in what we Kansans call a "toad choker" of a rain storm. The roads were flooded. It was more than the average rain storm, so I got home quickly and checked my new filter. It was soaked. No problems with how the car was running, but I will be finding some sort of splash guard to keep the bulk of the water from getting up there again.
Getting a performance diverted valve, like the one made by Forge, and installing it in the reverse configuration will further enhance the sound of the turbo.