The inside of a standard CAI is very smooth, causing very little air turbulence from the filter to the throttle body.

Your idea would be good for a few HP, with everything mounted correctly, but not as much as a smooth straight pipe. Max. flow can't be achieved with the ribbed flex tubing (if your car has it)..

Here's a number of cost-effective things you can do.. 1- slap a K/N right on the end of the intake pipe, where the airbox is.... 2- get an ebay CAI or short ram (they actually work quite well) 3- use PVC piping to route incoming bumper air to blow on the filter (doesn't work as well, and hard to do)

Personally.. I'd go with one of the nicer ($70ish) ebay CAI's... I've never heard a bad review of them. You won't get as much out of it as, say, an Iceman or comptech, but its still a better sound and more air moving.