I finally made a ram air duct for my car using a few threads from this forum as my starting point.
First I took a 4" rigid aluminum dryer vent:
Then I took a 4" PVC thread adapter:
With a little work I inserted the thread adapter into one end of the 4" duct and secured it with a bandclamp.
Then I removed the airbox, the two plastic shields below the engine compartment as well as the front portion of the driver-side brake duct.
Next I inserted the threaded end of my duct into the bottom side of the airbox and secured it with a 4" metal threaded ring as follows:
I then cut off about 8 to 10 inches from the other end and curved the 4" vent towards the bumper vent.
After fitting it perfectly I removed it and spray-painted it with flat-black, quick-drying paint.
Here's what it looks like after putting everything back together:
The paint scraped off of the end as I secured it with a zip tie so I put a couple pieces of electrical tape to hide the shine parts and prevent further scraping from daily driving.
Here's what it looks like from a distance:
It's pretty hard to see unless you're looking for it and walk up close.
It does feel stronger but I don't have numbers to back it up. I'm hoping to do some tests with my GTechPro Comp. soon.