(these aren't actual numbers but demonstrate the concept)
Lets say you move the accelerator by 12* resulting in a 1.2volt output which translates to 12% throttle.
The pedal commander is now placed in the middle:
You now move the accelerator by 12* resulting in 1.2volt output which the pedal commander intercepts, then turns into a 1.8volt output which translates to 18% throttle.
Indeed, that's the basic principle. However, it is no sham product and it is not the same as pressing the pedal faster.
Many cars, especially SUVs, have a built in throttle lag. It makes tha car easier to drive for the middle of the road driver and helps saving fuel in stop and go traffic. You can't remove the throttle lag by pressing the gas pedal faster.
To be honest, the Kia Stinger is already quite responsive in Sport mode. However, if you want it to be even more responsive, the XLR does a good job. You can also make the other driving modes more responsive.
I know these words won't convince you, but what about testing the product? We can send you one, so you can test it and decide whether you still think it is sham. Write me a PM if you are interested. (of course we would need a deposit).
The 'feeling' of faster throttle response wears off quickly and your left with a new point of failure in your throttle system and a potentially voided electrical warranty.
It will not "wear off quickly", but you'll get used to it. When you then lower the setting of the throttle controller you won't believe how boring your car in stock condition is. (maybe not the Stinger in sport mode, but generally speaking)
By the way, the XLR is the only throttle controller worldwide that comes with redundant security systems. We call this system Watchdog. If anything fails, you will still get the stock throttle signal. We never had issues with our previous generation, so it is not really necessary, but it'll give you a better feeling. We did it, because it enables us to get a TÜV Vehicle Type Approval in Germany (which no other company will get).