Trust "Airinx" and K&N intake filters
 

These are actually for the stock twin turbos on FD3S rx7's but can certainly be used on other projects. Coupler size is 2 3/8 to 2.5" ID. The Trust filters are easily disassembled and the media can be washed without removing the filter from the car. Of course we all know the K&N's are reusable as well.
All filters are used but in decent shape.

http://img143.imageshack.us/img143/9...1271gy6.th.jpg
http://img143.imageshack.us/img143/1...1272kf8.th.jpg
http://img523.imageshack.us/img523/5...1274wl7.th.jpg

Here's a borrowed image of the K&N units since I haven't taken any.
http://www.pettitracing.com/rx7/imag...take_upper.jpg

$35 shipped for either set
paypal preferred to morganf1@charter.net