Alex,
The 4" filter will attach to the hub of the 45*. You don't need a piece of pipe for that.

Relocating the IAT isn't "tricking" the PCM. It simply keeps the sensor from coming in contact with parts that are exposed to the engine heat, which in a sense could allow it to read higher temps than you are REALLY receiving.

People that talk about "tricking" the PCM usually have a resistor in the place of the sensor, giving the PCM a constant IAT rather than the sensor telling the PCM what it sees.

My IAT sensor is located way up in front of my filter. There are times when I still feel the need to trick the PCM because of having a Black car, and track temps. It would be more so if the sensor was mounted in the engine bay.

I agree with this too. Plexi looks pretty, but it's not a great insulator.

One little note if the apearance of the pvc is offensive the best I've found to paint it with is truck bed liner spray looks and is pretty durable.Chico.

I had planned on the whole box being made of the Plexi glass, and keep the top open or see through, and insulate the remainder of it w/ the reflective insulation. Maybe paint the whole box, w/ the exception of the top. I was thinking something similar to the thrasher box, or what Chico has.

But my elbow is 3" so the cone wont fit directly.
And the elbow is too short, the cone would be too near the engine. I bought a tube of 7" to connect the cone and a copler of 4-3"

Your material is not what I typically see then. Usually it's a Schedule 40 PVC which has a hub that is 4" in diameter to mate to a 4" filter, and the other end is 3.5" diameter to mate to the rubber coupling.....I assumed you had the same.
Can you take a picture of what you have?

ok, so i finally got it done and in the car. i still have some work to do on it, but at least it is finished. im not entirely happy about the overall finished product, but that is my fault. i did not put much thought into it, just went after it.

i did end up making it out of plexy and used aluminum angle to tie the corners together. ended up using too small angle and some of the corners did not hold together very well so i am going to go back over it with aluminum tape and see how that turns out.

i do have some pics and if i can get it together a rough, and i mean rough, diagram of the cut list. i used a cardboard template and once i was happy with that i cut the plexy and them made the drawings, ended up doing some further cutting and never made new diagrams. but what i have is a good starting place if i can get it all scanned to my computer. right now i am still having some computer problems, got a virus that totally screwed the hard drive or boot process, but as soon i get it back and everytihg running again i will try to get it all posted.

Good, now you know what areas need to be worked on and your second version will be much better.