There are two things about the Greddy turbo kit that I'm not wild about--the sponge air filter and the fact it's sitting exposed to the hot engine bay air. Since it's directly in front of the fresh air duct it isn't that bad when the car's moving but at slow speeds or idle it's sucking in lots of hot air. That can cause light engine pinging (aka detonation) which is never a good thing. Although enclosing the filter in the stock airbox restricts the air flow, most of that air will be cooler which is a good tradeoff.

Step 1: Unplug the MAF sensor harness.

Step 2: Loosen the connecting hose and remove the MAF housing and air filter.

Step 3: Attach the bottom portion of the stock airbox.

Step 4: Reattach the MAF housing and air filter.

Step 5: Trim the top portion of the airbox. That short sentence took me a couple hours of trial and error.

Step 5a: Start by trimming flat the pipe that connects the air box to the stock MAF sensor housing. I used a semicircle of ABS to cover the opening.

Step 5b: Cut a rectangle out of the back of the top cover for the intake to fit through. The rectangle will allow some hot air through but it will be a lot less than before and it's hard to make a tight fit around the pipe.

Step 5c: Attaching the cover is always problematic and trying to shoehorn the Greddy filter inside makes that worse. I found notching the flange around the bottom connectors (circled in red) makes it a lot easier.

Step 5d: If you use the Airnix filter you need to dremel, sand or otherwise cut part of the baffles (circled in green) to gain some extra space. Since I don't like the Airnix filter I recommend skipping this step and using a K&N filter instead.

Step 6: I'm actually not a big fan of K&N filters either. Despite their popularity independant tests have shown they don't have good flow rates and let larger particulates through compared to other brands. Having said that they're still better than the Airnix filter and the K&N Universal X-Stream Clamp-on (P/N RX-4120-1) will fit in the small space available.

Step 7: Reattach the top cover and you're done. Here's a shot taken from behind the air box. You can see I used four screws to attach the ABS semicircle.

Another benefit of using the stock airbox is it allows you to attach the plastic engine cover if you want to really go stealth.