Lap3 Pro Tuner for 1.6T Elantra Sport with included spark plugs and inline fuse
Manufacturer web page: LAP3 Pro-Tuner V2.5 - Elantra 1.6T-GDI | LAP3
Install guide: LAP3 Pro-Tuner Installation Guide | LAP3 (I have a copy saved if this link dies)
Original purchase price: $998 USD Dollars

Selling my car, and therefore selling this tune kit separately. This was absolutely worth the money. My car (2017 ES Turbo) ran smoother, got better low end torque, and pulled more on the highway. I would say it probably adds 40HP, makes the car feel a lot closer to a GTI (not quite there) while still being significantly more reliable. I had the kit on the car for two years, I don't drive a whole lot so maybe 10-15k miles? Including the spark plugs since they're basically required for this kit, and they're ~$100 for all four. Easy enough to install, I recommend removing the airbox to get to one of the connectors, I spent the majority of the install time getting that one right.

I'll ship in the US for free