Acceleration and odd engine behavior after ABS Update

Hi
Just got my Prius a week ago, and have about 400Km on it. Took it in to get the ABS recall update done yesterday (Deler missed it when they did the PDI!!).

Since then I am noticing some odd behavior with the engine. When the ICE is running, it feels like a car with a manual shift would feel if the gear were too high for the speed (I don't know how else to describe it). I felt this a little initially, but it was insignificant, but after the update, it is running like that all the time. I am also getting a lot of feedback/vibration in the accelerator itself, and response to acceleration is more delayed, even when the ICE is running (though I understand some of this is just about getting used to the Prius, but it did not 'feel' this way for a week before the software update.

Anyone experienced anything similar?

The car did come with a tank of gas, and I found that it was manufactured in Jul 2009 (delivered Aug 27, 2010), so could it be the original engine oil gelling in there or old or bad gas? Though the timing coincides with the ABS update.