I considered just the K&N drop in, as well as the tube and drop in, however I ended up getting a CAI from Steeda. I suggest the CAI. I bought the no-tune version because I plan to keep the warranty for awhile, however when you do get a tune you just pull out the reducer in the tube and you're all set. I really like the way the Steeda looks under the hood as well. The install was easy, it add's some sounds, it looks great under the hood, and it does add some power, even if minimal. If in the future you do plan to add some performance stuff you'll want a CAI, so you minds well just grab one now instead of spending the money on the drop-in and tube, only to upgrade again.
K&N CAI or drop in filter? I ran a full K&N CAI on my previous vehicle, it was nice, but I like the Steeda on the Mustang. The Steeda also comes with the sound tube delete plugs. A CAI will add sound, it's more noticeable if you add it before an exhaust, however my Roush/X pipe is so loud the additional sound created from the CAI is mostly unnoticeable. It probably added a few RHWP, and looks really nice in the engine bay. I figure when I add a 350 manifold, tune, and headers in the future it will be more beneficial then.
For the record, if you go drop in filter there are better choices than K&N. They dont filter well and you can over oil them. I'd recommend a dry filter like AEM.
I thought that too, but it's just the small resonator? that you cut off the factory snorkel. The snorkel is not permanently connected to the air box so you could always get a new one for a few dollars at most. Nothing is modified on the stock air box itself and it can be put back on at anytime. From all accounts I've seen, a no-tune CAI will not effect the warranty, which is why I bought one, I like keeping my warranty.
