How to build a cold air intake?

My buddy built one for his little Honda, I was curious if I can build one for a trail blazer and what all that intels

The first thing you need to do is find a source of cold air. By cold air, I mean any air not drawn from inside the engine bay. Oh look at that, the air that's drawn into the stock box comes from outside the engine bay. Congrats on building yourself a cold air intake.

Read this first

http://ricksfreeautorepairadvice.com/cold-air-intake/

Lol Ron, awesome. Yeah, go ahead and have a company replicate what is already on your vehicle, and you'd end up with exactly what you want, which is what you already have. OEM's aren't stupid. People who buy into the "cold air intake" fad are the idiots who don't understand engines. Go ahead, do the research yourself on how air and fuel interact, and how the engine works. You'll know ten times what your buddy does, obviously.