New ST Owner from St. Louis, MO

hi local guy.
You can get a open end air filter like Green, Cobb, or Mountune, and get some intake/by-pass valve whoosh noise when you shift.
I'd recommending picking up a dead pedal to save the carpet on the left. Boosted By Design makes a nice one, there are others available.
If you want the exhaust to sound like it should from the factory without getting too loud, and without breaking the bank, have a muffler shop do a resonator delete. I plan on doing one once I get my car.
We'll have to get together some time.

https://www.boosteddesigns.com/collections/2013-14-ford-focus-st/products/boosted-designs-dead-pedal

Hey...I'm local too. Currently fighting with the dealer to find me a car. Made a deal, they had to do a dealer trade, and then that dealer refused to trade. Now I'm caught up in the hatch recall matter anyways. uuuggg!

Welcome! Check out the STL ST/RS group on Facebook, always stuff going on here and lots of active members that can help you with upgrades! Also, Panda Motorworks is local and well-regarded in the community if you're looking for a tuner.