If you need justification do what I did. explain how the part you're asking for will make the car safer. CAI makes it more responsive in case you need to quickly get out of a tough situation.
Ha! This is how I explained to Jodi me "needing" to get a turbo. I will rarely ever pull out in front of traffic, and she hates it. So I told her if my car had more power I would pull out into traffic more, thus sacrificing several thousand dollars to make her happy. Don't think it worked... lol.
old: 2002 ZX5//current: 2006 ST