Ok im not gonna buy a hole K&N cold air kit cause its the same thing as the stock... I took the stock filter and the little platic thingy off and there is about a 3/4 inch lip there were the stock fliter fits but is that enough to mount a 4 inch cone filter on???
The rubber inlet tube is corrugated, thus interrupts airflow after the MAF and to the TB. You hear guys say that different materials resist heat better, but honestly the the air hitting the tubing isn't moving slow enough to feel the effects of a heated surface. But, to your original point, you will feel a difference between a CAI and simply adding a K&N. You could simply cut the shroud around the filter and leave it exposed, but do not cut the metal strap looking thing. YOu'll need that to fasten the filter to the MAF housing. I myself think its useless to get a CAI if you do not install a new MAF, TB, and plenum.
You could just do the open concical air filter like you're talking about, or, you can do the K&N FIPK setup which is what I recommend. I've had three different setups on my car. K&N air filter w/o silencer, BBK CAI, and the K&N FIPK. Out of the three, the K&N FIPK beats the other two hands down. The only draw back to the K&N FIPK system is its so damn expensive, however, it is about the best cold air kit available for our cars.
I have the UPR CAI for like $119 shipped...Had BBK bottom half and didnt like it..Seems like the UPR reaches farther down in the fenderwell than most kits do also...and you can really hear it when you bury the throttle!