The Photo's Referenced in this DIY is performed on a 98 Audi A4 1.8T Quattro.

This is a Simple Air Box Mod to allow cold air to be drawn into the Air Box.
The Air Gets drawn in before your MAF Sensor so there won't be any issues. Some of you will have concern about Water getting into your air box with this mod. Several people that have done this mod have had no water get into the box. I've tested it several times in heavy rain storms as with the others that did this mod. I have to give credit to "beer mod" on audiforums.com for this DIY.

First you need to start by pulling your airbox out of the car. Disconnect all electrical connectors that goto the box to simplify the removal. Once you get Air box lid off, it is pretty quick and easy from that point. Remove the one bolt holding the bottom portion of the air box in and just pull it up. There are two rubber gromets that hold it in on the bottom.

Now that you have the air box removed refer to the images for instruction:
(If there is technical difficulties with the images here are the directions - With the lower part of the air box out of the car you can see were the fender well lining is at. If you place the box back into the car you will notice how the fender well and air box meet perfectly at the contour of the fender. This is were you will cut your air box. Use a dremel tool or similar to modify it like below. (Wear safety Glasses while cutting the air box section)



Now after you have cut out the section of your lower air box, fit it up into the car and use a marker to trace out the area onto the fender well. Then i chose to use a 3/4" Bit to drill holes. Take the box back out of the car and now drill a bunch of holes into the fender well inside the area you traced.



Now fit up your lower air box into the car and you should have something similar to the image below



There are several different variations of this mod out there, And everyone will have something that they can add to the mod. A few suggestions that alot of people choose to use it getting a peice of screen (lowes, homedepot, hardware store, etc.) and cut it out slightly larger then the area drilled on the fender well. Use double sided tape to keep it on the fender. This will further insure that water will not get "splashed" into the box.

You can also get yourself some window weather stripping foam from lowes, homedepot etc. It is sticky on one side and apply it to the bottom of the air box to create a nice seal between the fender well and bottom of the air box so you do not suck any "hot" air from the engine compartment into the intake.

Another Safety precuation is to drill a few small holes into the bottom of the air box at the "lowest" point to create a drain in the case that water would find its way into your air box. Getting a K&N Air filter will also help out with any fear of water entering the box. The K&N Filters have oil on them which will propel water better then a stock paper filter. I did this mod first with a stock filter and later on upgraded. I had no issues at all with a stock paper filter.

Conclusion:

I found this mod to be excellent for the cost. It ran about 10$ Total for me, with a peice of screen, weather stripping and double sided tape. You could virtually do this for free if you don't want to add the screen and stripping. The Mod was definatley noticable on power gains and not to mention you can hear the engine growl as you accelerate. Best part is i did not spend 300$ on a intake kit.

Hope you all find this DIY Mod Helpfull.