I picked up the car tonight after the KIA dealer serviced it. There is a noticeable increase, from the day I bought the car, in throttle response, acceleration and the woosh sound from the cold air intakes. The tach is now rock steady at about 600 RPMs and the CEL is off. So what did they fix?
According to the invoice the service advisor gave me, the technician found code p0106 for "manifold pressure sensor performance." They found debris in the throttle body which they cleaned. They also performed an "adaptive value reset."
They also said there is no evidence of coolant leaks and the engine oil is not overfilled. They did not charge me for the service.
Strangely, the black plastic tray under the front of the hood in the engine bay is now stained in multiple places from what appear to be drops of some type of fluid they must have used. I was not able to remove the stains with a wet paper towel.