What is this?
 

I never noticed this tube coming off the intake. Where does it go?

It's called an 'Appendix'.. much like the one we all have in our bodies. And like the one we have in our bodies, it can play up! Noise and other foul odours can be attributed to it!!

If you are not trolling asking that, it's usually referred here as "soundtube". To pass extra noises into cabin. Some like it (due more engine noise inside w/o bothering others outside), some not (calling that sound artificial, and it passes in also roadnoise), and plug it off (via eg. glovebox cig lighter port cap), or remove this soundtube (for very slight weight savings and some cleanup of engine bay) & plug it's port at intake.

Nope, not trolling. I don't own this car yet. Just noticed the sound tube missing from a lot of forums and videos. So this is that sound tube... So, it's metered air being piped into the cabin for sound? I'm sure there's a checkvalve to prevent any dirty cabin air from getting sucked into the throttle body.

I love mechanical engine sounds. My WRX had this stupid milk jug to muffle the intake sounds.

I swapped out my OEM air filter housing for a CAI but left the sound tube, however, it's still plugged in but blocked.. no sound into the cabin, I prefer this... under the hood it all looks normal.

It is not an open tube. From dodgy memory there is a resonator/membrane at the end of the tube in the cabin that acts as a speaker cone.

https://www.ft86club.com/forums/showthread.php?t=35371

Now I see all the fuss... "Artificial sound," except it's piped into the real sound lol. I'd personally love more.

With speaker tube engine bay an unholy mess.
Without speaker tube engine bay neat and tidy. Just like my forum posts.

It is artificial sound that is generated from the real sound.

It works on the same principals as a kazoo.
https://www.rexlondon.com/sites/dotc...oo-28324_2.jpg

And sounds just about as good as one.

I disagree a bit. It may not sound very well, but without it (and 100% stock exhaust) it sounds even worse, dull, lifeless. Yes, i know, that power/performance is completely same, but after testing with plugging it off, i reverted. Even if it's just subjective placebo feel, car felt slower & less powerful :).
I do agree though, that good aftermarket catback and sountube-delete will result in much better and more pleasant sound, but it costs .. slightly more. :)

I'm planning on going the Tomei header/exhaust/tune route as this will be a summer/weekend toy. I'm probably leaving the stock airbox in there for ease of maintenance and access to the MAF and filter.

It is one of the dumbest things ever, just short of BMW piping fake engine noise over the radio speakers.

Sapphireho: unfortunately that's where world seems going to, with cars required by law laguna-seca like muffling and choice differing only in which specific way fake sounds will be produced. Yes, bmw's playback on stereo is another way. Choose your poison :).
Though madness goes other direction aswell, weren't some US states requesting for hybrid and electric cars to generate fake extra noises to outside, so that it makes pedestrians more aware of cars, no?

Since you mention it... [ame]https://www.youtube.com/watch?v=00LPlHDP98Q[/ame]