New prius

I have a 2010 Prius II I just purchased from my local Toyota Dealer with 45,000 miles, and new 195/65-15 Yokohama AVID Ascend tires on it. I have put a little over a 1,000 miles on it. I read a lot of posts that people are having trouble with the way the car handles at highway speeds and adding anti sway bars and other mods. I can take mine out on the interstate at 75 mph with 1 hand on the steering wheel and get a very comfortable and steady ride. No wobble shimmy or anything . In fact it handles better than my Honda CRV I traded in on it. Im beginning to wonder if the previous owner added some Mods to the suspension . This is our first Prius so I wasn't shire what to expect.