reports suggest "an improved TPS throttle position switch but Hyundai is unaware

This should set a code and check engine light. Have you replaced the TPS yet? Alex

Throttle position sensors fail all the time without throwing codes. It's like this: TPS reports the position to the PCM, so no matter what position it reports, the PCM just accepts it. There are many caveats to that statement, but that's possibly what you have going on. The other thing.... the pedal could do the same thing.

I could not find any info on an updated TPS. The car also has what Hyundai refers to as the Accelerator position sensor (APS). Its basically the sensor at the pedal to that receives driver input from your foot. This position does need to correlate with the TPS reading at the electronic throttle body. If it doesn't it can throw a code but does not always do so. At the end of the day I foresee another trip to the dealer if the problem persists. This is going to be a little outside the scope of an online diagnosis especially considering the dealer couldn't figure it out on the first try.