Space Or No Space
#4
I saw one where a guy had drilled a hole and ran the pipe around the radiator, and rotayman88's staged upgrade list in the FAQ said that he saw a gain of 6 rwhp on a car like that, so it just depends on if you think it's worth it.
#10
My idea, while not an actual cold air intake in your definition, would be making a cold air box in the bay, then routing cold air from the unused ducting in the front bumper using a divider to keep the air from moving to the radiator.
Heres a pic of what I'm talking about.
Heres a pic of what I'm talking about.