All car manufacturers advertise HP at the crank, meaning that is what your engine produces. However, due to drive shafts, transmissions, etc, you will lose about 30hp through all of that. So when KIA advertises 365hp, at the wheels, at most, you are getting about 335hp. This is not false advertising. The laws of physics just are. (Except in my pocket universe which I won't share because it's only big enough for me!)
Remember: The easier your car can breath in (air intake) and exhale (exhaust), the more power your engine can make. With a little bit of money (we don't know the cost, really, because there is no aftermarket in the US yet, hehe), time and a little know how, you can easily gain 10-20 horse power without getting a tune.
There's what's called your 'butt dyno' (you sitting in the drivers
seat and stomping the gas) and usually you can't feel 5-10hp of difference, but you know it's there. "My butt dyno says I gained a few horses!" And there's a true dyno, where they place the car and big steel rollers and hook up all sorts of probes and wires to the car and then stomp on it. A computer will take in all the readings and calculations and then display horse power and torque at the wheels.
Everyone's definition of a Tune is different. In my opinion, a tune is when someone hacks the ECU (electronic control unit) of a car and is able to change the default manufacture settings in order to increase/decrease air to fuel mixture, boost, etc. Something you plug in to trick your car into thinking it's not getting enough air flow, to me, is not a tune. Then you have a 'canned' or 'bench' tune and a custom tune. A canned and bench tune are the same thing. This is where someone hacks an ECU and determines the best average settings of a car with so-and-so modifications and sends that out to whoever buys their tune. A custom tune is just that, custom. This is usually more expensive as it requires time on a dyno in order to read the output of your car and makes adjustments on the fly, runs your car again, makes adjustments, etc. etc. etc. until your car is purring like a kitten or roaring like a lion!
Tunes come in stages. Stage 0, 1, 2, 3, etc. The higher the stage, the more aggressive the tune. Most drivers will opt for a stage 0 or 1. These are mild tunes and usually adjust air-fuel mixture, boost, and probably 100 other different small adjustments that I will probably never know about.
Stage 0 is very mild and probably cleans up air-fuel mixture and other things, no modifications is usually required.
Stage 1 tune usually nets about 40/40 (hp/torque) and probably will require a few bolt-ons, such as a bigger cold air intake; probably a few hundred dollars of various parts replacement and usually just require removing a few bolts to replace, hence the term bolt-ons. The bolt-ons plus the tune may net about 60/60 over all. Depending on bolt-ons you put on your car. When I had my Veloster Turbo, my net gain was 40/35 with a stage 1 tune and just a cold air intake.
Stage 2 and beyond are usually for those with interest of putting their car on a track (drag or otherwise), bragging rights, or for the fun of it! They are a LOT more aggressive and usually requires more extensive work; chassis stiffeners (sway bars), cat back exhaust (replacing exhaust from the catalytic converter to the muffler and exhaust tip, bigger intercooler, forged rods and pistons, replacing the smaller turbos with bigger ones, etc, and can get real expensive. These can also cause extreme damage to the engine if proper care hasn't been taken to prepare the engine for this kind of power. I've seen 1.6 turbos put out a net gain of about 170hp with major bolt-ons and a stage 3 tune.
Me, I'll have to wait to see what the after-market brings to the table for the Stinger GT before I do anything but woooo, doggie! I can't wait! I can easily imagine around 400hp with a few bolt-ons and a stage 1 tune. The problem will be after market support. It will take a little time for people to research and develop a tune and after market parts so I wouldn't expected to see anything major until about 6 months after the car is released, at least here in the US. Someone's gotta buy the car and then willing to blow it up while they try this out and that out and ooops! too much of this or too little of that and POP!
Oh! And just because KIA may advertise 20 city and 28 hwy (whatever they will advertise the MPG here in the states), remeber that these numbers are AVERAGE and under mild driving conditions. Altitude, humidity, heat, will always affect these numbers. And so does your LEAD FOOT! HAHAHAHA!