I used 3" tubing, and built a sheetmetal enclosure insulated with firewall insulation to reduce heat. I also built a small duct to go from the lower left grille opening to the air intake duct at the core support. The 3" tubing was a little small, but it was as close as I could find.
The FIPK replacement filter part # is in one of my old posts.
Mine is similar to thechief66. I just ordered the replacement filter. I had my local exhaust shop cut up two short pieces of 3" tubing that was scrap. Used a couple of hose clamps and plugged the hole in the end of the filter.
I left my lower box in, so the factory cold air duct from the grill continues to push cool air to the filter area.
My box doesn't look or likely work as well as thecheif's. My homemade box is literally cardboard from a box that was cut/fitted to help shield engine heat from the filter. My intent was to do a sheet metal enclosure and insulation, using the cardboard for a pattern. However, the cardboard has never been replaced.
Look up "projectmpg" for dyno information concerning this setup and a few other combos.