Is this a single pipe or duel pipe intake?
I think you need to be at least 3" to 4" for maximum efficiency (single pipe), otherwise I see no point to making up a homebrew CAI if your just gonna use 2-3/4" plumbing.
The reason for being that large is due to the distance the air travels along the pipe, this will created alot of friction drag in 2 3/4" pipe. And I'm sure you will have several 45-90 degree bends too.